Pool Dictionary

These are underground braces that support and stabilize inground pool walls and help hold the walls in place. The bracing for some inground pools may be adjustable, and the braces should always be made of the same material as the pool walls they are supporting.

A pool that sits completely (or almost completely) on top of the ground. Both the pool walls and water line of the pool are above ground level. Above ground pools are the most common type of pool. InTheSwim.com carries a large selection of above ground pools and soft-sided pools.

Filter rating meaning that 99.9 percent of essentially all of the particles larger than a specified micron rating will be trapped on or within the filter.

Items that are not required for proper pool operation, but instead make pool use more fun or improve pool safety, make it easier to maintain or more functional. The most popular pool accessories include pool cleaning equipment, steps and ladders, slides, pool lights and fountains. Search the various pool accessories from In The Swim.

Liquid (muriatic acid) or dry granular (sodium bisulfate) substance used to lower the pool's pH (toward a more acidic condition) or to lower total alkalinity levels.

A titration test used to determine proper amounts of acid (or pH decreaser) to reach correct levels. For example, to lower pH from 8.0 to 7.6, your pool may "demand" 2qts. of acid.p;

Also called a drain & clean, an acid wash becomes necessary if the pool has turned into the "black lagoon". This may occur if the winterizing process is not done properly, or if the pool has been stagnant for a period of time so that algae has taken over. If you notice scaly, man-phibian creatures splashing around out back, it's probably time to drain & clean.

Located on the top of the filter, often adjacent to the pressure gauge, the air bleeder is opened to release air trapped in the filter.

Also called a Spa Blower, this is used to inject air through spa jets, for increased jet volume. Modern air blowers are highly energy efficient and produce significantly less noise than in the past. Browse air blowers and other spa equipment at In The Swim.

An essential item for closing above ground pools, an air pillow floats in the middle of your pool under the winter cover and absorbs ice expansion over the winter, preventing your pool walls from cracking or splitting. Find and other pool closing accessories at In The Swim.

This is the stuff that causes your pool water to appear green and covers your pool’s underwater surfaces with slimy coating. Algae is an organic, simple non-flowering plant that thrives on light energy and grows through photosynthesis. Over 20,000 species known to exist.  Algae may form on your pool surfaces or it may bloom in suspension.  We typically know algae to be green but it may also be yellow (mustard algae), black, blue-green, or any shade in between. It may form separate spots or seem to grow in sheets.  Pink algae is not algae at all but a form of bacteria. Algae are living breathing organisms that need warmth, sunlight, and CO² to thrive.

A pool chemical with the sole purpose of eliminating algae blooms and preventing future algae growth in the pool. Most pool algaecides come in a liquid and are introduced into your pool water or filter system after the use of pool shock. You should always let your pool filter run 24 hours after using an algaecide.

Used to raise alkalinity when levels drop below 80 ppm. Alkalinity increasers are important water balancers that make controlling your pool’s pH levels easier, by buffering your pH against change.

Generally, these are pool chemicals or systems that disinfect, sanitize and clean pool water and pool surfaces without the use of chlorine. Alternative chemical sanitizers tend to be more organic, or naturally derived, while alternative systems like mineral purifiers, salt chlorine generators and ionizers. Alternative sanitizers are effective without the harsh side effects chlorine and bromine have like skin and eye irritation, hair discoloring and fabric bleaching or staining.

Also known as "alum" this chemical is used as a flocculent which attracts suspended particles in the water together (green or cloudy pools). Alum sinks everything to the bottom  which is then vacuumed to waste. A small amount of "alum" can also be used as a sand filter additive. 

This pool part is often used to secure pool ladders, rails, diving boards and other pieces of equipment to the concrete deck around an inground pool. Anchor sockets can be made of a variety of materials including plastic, brass and bronze.

A combination Ozonator and UV system, AOP devices first ozonate the water, then radiate it with UV light in the germicidal spectrum of 253 nm, which produces a particle called a hydroxy radical inside the chamber, which is one of the world's most powerful sanitizers. Not only a algaecide and bactericide, but it even removes biofilm and the strongest of waterborne pathogens. It sanitizes, purifies and clarifies the water.

see “Controls”

An automatic pool cleaner remove dirt and debris from pool surfaces without human interaction. There are three different types of automatic pool cleaners: robotic pool cleaners, suction side pool cleaners and pressure side pool cleaners. The biggest advantage of automatic pool cleaners is reducing pool maintenance time for pool owners or managers. The pool can be cleaned automatically by machine freeing up time for a person to do other maintenance items or clean via remote control (depending on the model) for a faster, more efficient pool cleaning.

The replacement of soil after digging a new pool. Placed in layers, tamped as they go, and soaked with water to allow full settling.

The process of cleaning a sand or DE pool filter, by reversing the flow of water through the filter to flush out the trapped dirt and debris.

Backwash valves are used to reverse the flow of water through the filter tank, to backwash or clean DE or sand filters. A Multiport Valve or Slide Valve (aka Push-Pull Valve) is commonly used. On larger commercial filters, a set of three or four valves are turned to accomplish the task.

Any of a class of microscopic plants having round, rod-like spiral or filamentous single cell or non-cellular bodies, often aggregated into colonies or mobile by means of flagella. Living in soil, water, organic matter or the bodies of plants and animals and being autotrophic (self-generating), saprophytic (digests chemicals already in their environment) or parasitic (living off a host).

Balanced water is the result when all of your chemical parameters are where they should be and thus balance each other. The key components of water balance are pH, Total Alkalinity, Calcium Hardness, and Temperature; as measured using the Langelier Index of water balance.

A type of directional valve, with a hollowed out ball inside, which is turned with an external handle to control water flow.

Those chemicals of alkaline nature which will counteract the pH of an acid, eventually neutralizing to 7.0. A base is the opposite of an acid, and is used to lower pool pH levels. Common bases used around the pool would include Soda Ash, Sodium Bicarbonate, Sodium Carbonate, and Sodium Sesquicarbonate.

A titration test used to determine proper amounts of base (pH increaser) to reach correct levels. This type of test is done with your pH test sample. Adding a second reagent dropwise, and counting the drops, you can refer to a chart to determine the amount of base needed (demanded) by your pool water.

This is a piece of plastic tracking with a slotted lip that fits to the top of your above ground pool’s steel wall. The beaded edge of your vinyl pool liner locks into the slotted lip of the bead receiver, creating a secure mounting of the liner.

A colorless, solid organic compound which dissolves in and sanitizes pool water. Biguanide, or the polymer PHMB, is chemically similar to household peroxide, and it is the only EPA-approved non-halogen pool sanitizer/disinfectant available. Biguanides have been reported to be easier to use, with less chemical level testing, and less adding of chemicals. The water doesn't smell of chlorine of course, and the reduced surface tension gives it a smoother feel. It doesn't degrade with sunlight, temperature, or changes in pH levels like chlorine. At recommended concentrations, biguanides won't irritate the skin or eyes and can't corrode pool equipment. Biguanide is not compatible with chlorine and bromine products, and is the only complete alternative sanitizer system.

Plumbed into the spa return line, blowers inject air in the pipe to produce fun bubbles and to increase the power of the spa jets, to create a hydrotherapy effect in the spa.

Pressure pool cleaner booster pumps are secondary to the filter pump. A booster pump is used to power a "Pressure Pool Cleaner" such as Polaris and other cleaners that connect to a dedicated return line.

When you shock your pool, the goal is to reach a high enough level of free-chlorine, measured in ppm, to break apart molecular bonds; specifically the combined chlorine molecules. When breakpoint is reached with sufficient additions of chlorine, everything in the pool is oxidized - success!

British Thermal Unit. A unit of measurement for the use of gas by a gas appliance. Pool heaters are rated by their output.

Your alkalinity levels buffers the pH, or increases its stability, to prevent rapid changes in pool water pH levels. The pH level in your pool are prone to big swings due to rain water, pool usage and swimmer loads, and proper levels of alkalinity helps prevent this, by buffering the water.

A bullnose edge is a half-rounded edge, used around the inside perimeter of inground pools. On vinyl pools, bullnose coping is the most popular coping and it allows a concrete deck to be poured right up to the edge of the pool. For gunite pools, bullnose coping stones are used on top of the pool wall, which help channel water away from the pool and provides a safety grip for swimmers.

Braces on the side of an oval-shaped above ground pool. Buttresses, also known as A-braces, provide structural support to pool walls and can stick out up to three feet away from the long sides of an oval pool. Most modern pools use a buttress-free or narrow buttress system with the buttress frame system being underground so the pool takes up less yard space. There are still some pools like the Intex prism frame pool that utilize a buttress system.

The level of total dissolved calcium in your pool water. Depending on the region you live, your tap water may be either too soft or too hard for your pool. The recommended calcium hardness level is 200-400 ppm. Add calcium chloride to increase calcium hardness levels, or dilute with fresh water to lower calcium levels.

Known as scale, crystalline deposits of calcium may form on your pool surfaces, equipment, or even line your pipes like cholesterol in your arteries. Properly balanced water can prevent scale from forming wide scale. Many pools have scale depositing as thin sheets of scale on the surface, but on a white pool it may not be noticeable.

The flaked calcium salt used to raise levels of Calcium Hardness in your pool water. Also good for melting snow and ice.

A titration test is used to determine levels of the mineral calcium dissolved in the pool water. The best range for Calcium Hardness is 200-400 ppm. Some pools may be much higher in certain hard water parts of the country. Calcium Chloride is used to raise Calcium Hardness levels when the water is too soft, but there is no reliable chemical that will lower calcium levels.

A powerful form of granular chlorine that is used as pool shock. Cal Hypo is the most economical choice for pool shocking, and has 65% available chlorine, or 73% in our Super Pool Shock. Fast acting and pH balanced, Cal Hypo is the most popular pool shock in America.

The Capacitor is the battery for your pool motor. It provides the energy needed while starting, to reach 3450 rpm quickly. Replace your capacitor when the shaft can be spun freely with a wrench or by hand, and when powering the motor, you hear a 'buzz' or a 'hum' from the motor, but no impeller movement. Replace your old capacitor with an exact match to the 'MFD' number on the new capacitor.

One type of filtration, a filter cartridge is a pleated, porous element through which water is passed through. They are not backwashed, but are removed from the tank to be hosed clean. After 12-15 cleanings, the fibers loosen and no longer perform well, and are replaced with new.

The edge where the top of an inground pool wall and the surrounding deck meet. A cantilever coping is when the deck is either poured (with concrete) to make a finished edge just inside the pool wall or with pavers installed with the same finished edge as poured concrete. Traditionally, a cantilever coping is used for fiberglass pool shells, but this attractive type of deck finishing is now used on inground pools with vinyl liners as well. The cantilever coping is poured using Styrofoam forms, and the vinyl liner is placed in a channel under the coping for a highly professional look.

A general term used to describe the behavior of voids or bubbles in a liquid. Cavitation is usually divided into two classes of behavior: inertial (or transient) cavitation and non-inertial cavitation. Inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave. Such cavitation often occurs in pumps and impellers Non-inertial cavitation is the process where a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field. Such cavitation can be observed in pumps.

When water has worked open "holes" in the sand and most water is streaming right through, without being filtered.

A one way flow device, where water can only flow in one direction.

Sometimes referred to as a chlorinator, or simply “feeder,” a chemical feeder is a quick, efficient way to distribute chlorine or bromine evenly into pool water. The chemical feeder holds the sanitizer and automatically dispenses it at the rate you specify for your pool size on the feeder. There are three types of chemical feeders including in-line, off-line and floating feeders. These different feeder types have their own advantages, but they all reduce maintenance work for the pool owner.

The chlorine molecule is strongly attracted to nitrogen and ammonia. When these two combine they form a chloramine molecule, also known as combined chlorine. These are undesirable, foul smelling, red-eye making, space taking compounds that require shocking the pool water to remove.

The most common and economically priced type of pool sanitizer. Pool chlorine is effective at eliminating dangerous pathogens like bacteria and other contaminants to make pool water safer for swimmers. Chlorine comes in many different forms including tablets, sticks, granules and liquids, and it is rather simple to use for regular pool maintenance.

The quantity of free available chlorine removed during the process of sanitizing. The amount of organic and non-organic material contained in the water will demand a certain level of oxidizer to be destroyed.

This piece of pool equipment converts ordinary salt into chlorine, to sanitize your pool water. When your pool pump pushes the slightly salty pool water through a chlorine generator, electrolysis converts salt into hypochlorous acid, the exact same compound produced when you add chlorine to the pool. Also known as Salt Systems, chlorine generators are easy to use and very effective at removing contaminants and pathogens. Saltwater pool owners also enjoy fewer odors, less eye, hair and skin irritation, and no bleaching of swimsuits.

A vital sanitizing component for your pool water that is often-times a pre-packaged, higher concentration of granular chlorine used to raise the free chlorine levels of your pool to help eliminate contaminants like algae and bacteria from the water.

A polymer pool chemical that attaches to suspended particles in your pool water, a clarifier is a chemical used as a coagulant of suspended micro particles. It helps the filter by clumping smaller particles into filterable sizes. Also called coagulants, Pool Clarifiers are often made of ammonium chloride with a highly positive charge density. The positive charge in the clarifier quickly coagulates with the negatively charged particles in your pool water, creating larger “clumps” that are easily removed by your pool filter.

A packaged kit of pool chemicals that usually include everything needed to keep pool water stabilized and prepared to be covered throughout the winter. Closing kits usually include chemicals like algaecide, shock, oxidizer and stain preventer. Most kits are available in a range of sizes to remove guesswork from applying the chemicals to pools with

The process of preparing your pool water and pool equipment and then covering your pool for the winter months or any prolonged span of time of no one using the pool. A typical pool closing includes cleaning all pool surfaces, balancing the pool water with winterizing chemicals, draining or plugging lines, and securing a winter cover over the pool to protect the pool throughout the winter and make it better prepared for an easier spring opening.

A pool water condition that appears milky or opaque instead of transparent and clear. Cloudy pool water occurs when particles and contaminants are suspended in the pool water reducing clarity. There are many causes for this happening including having high pH or high calcium hardness levels in your pool. Cloudy pool water is rather easy to rectify using the proper water balancing chemicals or a clarifier, depending on the cause of the cloudiness.

When pool water takes on a hue or tint that is unnatural or not caused by dye additive. Most unwanted colored pool water occurs with the presence of stain-producing metals like iron, copper, manganese and cobalt. Pools filled with well water and properly treated with chemicals tend to have slightly colored, yet safe, pool water. Using a pool clarifier often removes the color from your pool’s water.

Chlorine that is no longer free and active, also called chloramines, caused when chlorine combines with nitrogen or ammonia. Measured combined chlorine is the result of subtracting Free chlorine from Combined chlorine. When high levels of combined chlorine are measured in your pool, a strong odor is present and swimmers eyes become irritated. Use pool shock to reduce combined chlorine by raising the chlorine level to 10x the amount of combined chlorine, to break apart the compounds.

An inground pool coping that sits atop and protects the pool wall. Usually constructed of aluminum, a concrete receptor coping allows concrete to be poured right up to the edge of the pool with a channel on the bottom side to secure the top edge of the pool liner.

A pool chemical that protects pool chlorine from being destroyed by UV rays or sunlight. Pool conditioner is sometimes also referred to as stabilizer or pool stabilizer.

Relatively new technology that allows you to manage a range of pool equipment and accessories like pool heaters, pump and filter system timers, pool lights and salt generators. Automatic controls allow for easier, more efficient maintenance and operating schedules and can detect then react to system anomalies such as a change in vacuum pressure or water freezing conditions.

The finishing cap for the top edge of an inground pool’s walls. The coping is mounted on the bond beam, covering and concealing any pool wall steel reinforcement while preventing water from getting behind the pool shell which could deteriorate the ground around the pool eventually leading to failure. There are several different types of inground pool coping including poured concrete, stone, brick and precast concrete, all with a range of textures, patterns and colors.

Long pieces of plastic that secure your vinyl overlap liner to the top of your above ground pool wall. Coping strips also protect your liner from being damaged by your pool’s top rail.

A degradation or deterioration of a metal’s property due to interaction with the environment or a chemical process. In a pool, unbalanced or unchecked pool chemicals, mostly pH levels, can cause any metal that comes in contact with the water to quickly corrode. Corrosion can be costly by destroying stainless steel ladders, hand rails, pool pump components and even copper heat exchangers.

Plastic fasteners that firmly grip the top rail of your above ground pool to tightly secure your winter cover in place. These clips are easier than a cable and winch to install, and they are great at keeping wind from getting under your winter cover and causing damage.

Small, submersible water pump designed to remove water due to rain or snow melt off of winter covers and solid safety covers. Most cover pumps are electric and operate by plugging the unit into a wall outlet, but there are some manual cover pumps available as well.

A granular chemical added to the pool water which provides a shield to chlorine for protection from UV radiation, which disrupts the molecule, destroying its sanitizing ability. Also referred to as Pool Stabilizer/Conditioner.

A bag that collects pool debris like leaves, twigs, blades of grass, bugs, etc. Most debris bags are made of mesh to trap particles but let water out, and they are usually attached to automatic pool cleaners, more specifically pressure-side cleaners.

Support for an above ground pool deck. Extra bracing, or support, is usually needed for free standing vinyl pool decks and even wood decks that span around the pool’s walls.

Known as Di-Chlor shock, it is the only stabilized form of shock, useful for shocking during sunlight hours, or for treating fountains and water features with weekly sanitizer. DiChlor shock like our Di-Zap, is an oxidizer, bactericide, algaecide, and cleaning agent that reacts with water to form hypochlorous acid.

A powdery pool filter media used in diatomaceous earth pool filters. Diatomaceous Earth, most often referred to as D.E., is a soft, sedimentary rock that is usually 80-90% silica and occurs naturally in the earth. D.E. powder and filter systems are more efficient at filtering pool water than sand or cartridge filters, capturing particles as small as 3-5 microns in size.

The demand that your pool has for dirt. This level is inversely proportional to available time for cleaning. If you remove the dirt from the pool, you have created a dirt deficit, and the pool will actually suck dirt out of the air to maintain its dirt demand. :-)

The elimination of harmful or illness-causing bacteria, contaminants and organic material from pool water and pool surfaces. Also known as sanitizing or oxidizing, there are many pool and spa sanitizing chemicals available to perform this important duty.

Used in a twin port skimmer, a diverter allows the operator to manipulate the amount of flow from the main drain and skimmer to the pump.

A method of testing for chlorine levels in the pool water. Unlike OTO test kits, DPD testing allows determination of total and free available chlorine levels which through subtraction gives us combined levels.

A 90 or 45 degree plumbing fitting. Used where your pipes take a turn.

A more stable, easier way of getting in and out of both above ground and inground pools. Pool entry systems are more like stairs than a pool ladder, having gradual steps to use and hand rails to hold onto. These systems are made from a highly durable vinyl and also make for a great shallow-water seat for relaxing.

Currently enforced in Texas along with some counties and municipalities in California, this is maximum allowance of emissions to reduce pollutants released into the atmosphere created by pool heaters, heat pumps and other fossil-fuel burning pool equipment. Because of this mandate, there are now Low NOx and more efficient pumps and heaters available on the market.

The use of enzymes in pool and spa water treatment has come into its own in recent years. Having been around for ages, enzymes exist in every living (and dead) organism on the planet. They are used to break down organic matter, in fact, they actually consume organic matter in the pool or spa.Used in swimming pool formulations designed to break down and digest oils and organic debris in a pool or spa similar to the way enzymes are used in oil spill clean-up efforts.

The piece of finishing trim that covers the gap between where the pool ladder or hand rail and the anchor socket on the pool deck.

Process of the pool water’s surface changing to a gaseous, atmospheric state because of an increase in temperature. Dry climates with low humidity tend to increase evaporation. Most of an open pool’s heat loss comes from surface evaporation, and evaporation also can lead to a loss of pool chemicals. One of the easiest ways to protect against evaporation is to use a solar cover on a regular basis.

The gap between the pool deck and the pool coping stones. Very important to use caulking to keep the joint from filling with debris, and also to keep out water which can cause damage to the beam of a gunite pool.

A basis for indicating the resistance in a hydraulic system, equivalent to the height of a column of water that would cause the same resistance (100 feet of head equals 43 pounds per square inch). The total head is the sum of all resistances in a complete operating system. The principal factors affecting a head are distances, bends and turns, and the resistance caused by friction between the fluid and pipe walls, and being forced into impellers, filters, heaters and chlorinators. Add up all the resistance of a pool circulation system, and you have a total feet of head, which is used to help select the proper pump, with the use of a pump flow chart.

The main component of the pool pump and filter system that captures and traps particles and contaminants from pool water. There are three types of pool filters including sand filters, cartridge filters and Diatomaceous Earth (D.E.) filters. Each type of filter works in different ways, but the result for all filters is to keep pool water clear and clean for swimming.

A type of pool filter that is a physical barrier, rather than a media like sand or diatomaceous earth, made of materials that allow pool water to flow through pores while capturing particles and contaminants. There are many advantages to using filter cartridges including they are easy to use with simple installation and maintenance as well having a longer usable lifespan since cartridges can be removed, cleaned and re-used many times. There are various makers and styles of filter cartridges with many options usually available for the make, model and size of your cartridge pool filter.

The filter element component to a Diatomaceous Earth (DE) pool filter. The filter grid holds the DE powder that does the actual filtering of microscopic particles and contaminants from the pool water. Filter grids are replaceable and available individually or in full sets, in various heights to fit different filter sizes.

A finely graded material such as sand, diatomaceous earth, polyester fabric, or anthracite coal that removes suspended particles from water passing through it.

Also called the “Pump and Filter System,” the filter system is the entire group of components that operate together to rid pool or spa water of particles, contaminants and other impurities and debris. The filter system contains the pool pump, the pool filter unit (cartridge filter, sand filter or DE filter), and all of the hoses that pulls water through the skimmer, carrying it through the filter and returning the cleaner water back to the pool.

A type of pool accessory that allows a person or group of people to float on any body of water including a pool, pond or lake. Pool floats come in a vast array of designs from basic inflatable inner tubes to more luxurious and adjustable loungers made of high-tech, unsinkable foam.

Technically called “Flocculent,” is a specialized clarifying pool chemical, when added to cloudy pool water, clumps the suspended particles together so they sink to the bottom of the pool. Floc then needs to be vacuumed to waste. Floc the pool when water conditions are so bad that clarifiers and constant filtering are failing.

The chlorine that is still available to sanitize your pool or spa water. Free chlorine is usually the type of chlorine tested for when checking a pool for chlorine levels.

The quantity of water flowing past a specific point in a specified time (e.g. the number of gallons flowing through the filter every minute is GPM or Gallons per Minute).

The type of galvanized steel typically used for inground pool walls. G235 steel has a 14-gauge thickness (about 1.9mm) and coated with 2-3/4 ounces of zinc per square foot. The zinc acts as a rust inhibitor mainly for ground water that may get near your inground pool.

A gasket is a mechanical seal that fills the space between two objects, generally to prevent leakage between the two objects while under compression. Gaskets are commonly produced by cutting from sheet materials, such as gasket paper, rubber, silicone, metal, or a plastic polymer.

The type of valve that spins "lefty-loosey; righty-tighty, like a hose spigot. Commonly found to be leaking air or water.

A construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints (like those between tiles). Grout is generally composed of a mixture of water, cement, sand and sometimes color tint which is applied as a thick liquid and hardens over time, much like mortar.

Gunite is a brand-name of a concrete application process that pumps and sprays a concrete mixture through a hose and gun. Pressure sprayed Gunite is easy to use to create curves and special shapes, making it ideal for forming walls, steps and the floor of custom inground pools, along with bridges, dams, canals, locks, tunnels and pipelines. Gunite is pumped wet through the hose, while an alternative option ‘Shotcrete’, is mixed with water at the gun nozzle.

A member of the family of elements fluorine, bromine, chlorine and iodine.

That water which is high in calcium hardness and other salts which, as such, resists soap being lathered.

The amount of calcium and magnesium in the water in grains per gallon, (expressed as calcium carbonate). This level is important to control during distillation or reverse osmosis processes to prevent scaling. Each grain is equal to 17.1 ppm of calcium and magnesium (expressed as calcium carbonate). What constitutes truly "hard" water is subject to much debate and controversy. Proponents of water softening systems tend to call water "hard" which contains between 3 and 10 grains of hardness. This definition is supported by the American Society of Agricultural Engineers and the Water Quality Association, major supporters of the water softening industry. Water with 10 grains of hardness, is regularly used by consumers, with little or no adverse affect on plumbing or other household functions. Water, which approaches 15 to 20 grains is more in line with situations which require water softening or conditioning. Water with 3 grains of hardness and is termed "moderately hard" by these organizations is typically found in surface and spring water sources, far removed from what one would consider hard water sources.

A more energy efficient version of a pool heater. A heat pump does not generate heat, instead it uses electricity to capture warmth from the surrounding ambient air into an evaporator coil which then transfers that warmth as heat to the cooler pool water circulated through the heat pump via the pool pump. The heated water then circulates through the pool, returning to the heat pump, where the entire process is started again. Heat pumps are more efficient than pool heaters in terms of energy costs, but traditional pool heaters heat pool water faster.

A pool heater is the fastest way to generate warmer pool water. Available in natural gas and propane gas, the type of pool heater you use may greatly depend on the type of gas service you have available to your home. A pool heater operates much like the heater in your home by using a relatively efficient combustible (natural gas or propane), but instead of using heat generated from the gas to warm the air, pool heaters generate heat to warm pool water that is circulated via the pool pump and filter system. Pool heaters can greatly extend your swimming pool season, and in some climates, make swimming year-round possible and enjoyable.

The result when ozonated water is radiated with UV light, the hydroxy radical is a powerful sanitizer, and the result of an AOP system, the newest alternative sanitizer on the market.

The rotating vanes of a centrifugal pump; its action creates the flow of water. The impeller is shaft driven by an electric motor.

A swimming pool where the walls and water line are at or below ground level. An inground swimming pool is highly customizable in shapes, sizes, depths and finishes, and are available in three general types: fiberglass, concrete (which includes gunite) and vinyl liner. Each type of inground pool offers different advantages, with vinyl inground liners leading in low initial costs and smoothness of finish.

The process of constructing or putting in place a new pool or adding a new piece of pool equipment to an existing pool.

The hose connecting the pool skimmer to the pool filter and draws water from the pool to be rid of particles and debris in the filter.

A pool sanitizing system that implements copper and silver ions to rid pool water of bacteria and prevent algae growth. A pool ionizer is becoming more popular as an alternative pool sanitizing option and replaces the need for pool chlorine and other harsh chemicals. Nature2 and Frog systems also offer a different type of erosion ionizer, with copper and silver ions released in controlled amounts, and a no-stain guarantee.

A brand name of two-way and three-way valvse, which has simplified pool plumbing.

An above ground pool vinyl liner that is also called a Uni-Bead Liner. These liners have a bead that looks like a hook, or upside down “J” that rests on top of the pool wall under the top rail, generally offering more choices in styles and colors. Unlike expandable and overlap liners, no coping strip is needed when installing a J-Hook liner.

Used in spas and hot tubs to provide additional thrust into the hydrotherapy jets.

Rubber caps (female ladder bumpers) or rubber plugs (male ladder bumpers) which protect the pool plaster or vinyl liner from the sharp steel ends of the ladder rails.

Also called the Saturation Index, Mr. Langelier devised a system to determine water balance by assigning values to levels of pH, Total Alkalinity, Calcium Hardness and water Temperature. When all parameters are in balance, the water will neither be corrosive or scaling. The formula is "SI = pH + TF + CF + AF - 12.1."

A lightweight mesh cover that is placed over a pool’s winter cover designed to let rain water through while catching fallen leaves. The leaf net can then be folded up and removed to easily get rid of leaves during autumn.

A basket-like mesh that is attached to a sturdy rim that creates a wide opening. When attached to a telescoping pool pole, the mesh captures fallen leaves while allowing pool water to flow through to easily scoop leaves, other light debris and even small pool toys that have settled to the bottom of your pool.

An inline strainer that is used with suction pool cleaners, or when manually vacuuming pools. Used with a short 3 ft or 6 ft hose, the Leaf Trap has a large mesh bag to trap leaves before they reach the skimmer or pump, so you can vacuum longer without stopping.

The receptor at the top edge of a pool wall that locks in a vinyl liner. Liner extrusions are usually made from aluminum or a sturdy plastic, and they can be installed as a top mount or front mount on the pool.

Pliable plastic strips inserted between the coping strip and top rail on an above ground pool, locking a beaded vinyl liner into place. Liner lock also provides a professional, finished look to a pool.

A highly efficient combustion process used in certain pool heaters that greatly reduce nitrogen oxide emissions (a common pollutant) into the air. For a pool heater to be deemed Low NOx, it must prove to be high efficient with low emissions over the life of the heater.

Performance of regular upkeep on your pool to keep the pool and connected pool equipment functioning in a safe manner along with keeping a series of important pool chemicals at specific levels for pool water to be clear, clean and safe to swim in.

A form of winter or safety cover that is porous, allowing rain water and snow melt to drain into the pool while capturing debris during the time the pool is closed. A mesh cover eliminates the need of a cover pump and also saves money for spring opening by keeping the pool water level higher, reducing the need to refill your pool.

A sanitizing system for pools and spas that use minerals to destroy bacteria, pathogens and other contaminants from water. Most mineral purifiers employ copper and silver as natural sanitizers for clean, clear water.

The process of taking the winter cover off and cleaning your pool, treating the pool water with the proper chemicals, and connecting the necessary pool equipment to get your pool ready and safe for swimming.

Rubber rings of precise diameter and thickness, to seal up mating surfaces. Keep lubed with a pool lubricant and never use petroleum jelly. O-rings are used to seal up pump lids, diffusers and seal plates, filter tanks, bulkheads and valves, heater headers, chlorinator lids, valve lids, etc. I can't think of but very few pool equipment items that do not use o-rings!

Off-Line products are those installed off of the plumbing line. Such as an off-line chlorinator that is connected to the line via hoses, and not plumbed in-line like other models.

Also known as an ozone generator, this is a piece of equipment normally found on spas and hot tubs that combine an extra oxygen element to form “energetic oxygen” or ozone. The use of an ozone generator in a spa and hot tub setting is popular since ozone is a powerful, and natural, water sanitizer killing bacteria, mold, mildew, viruses and fungus faster than chlorine.

A piece of safety equipment that gives audible, and sometimes visual, alerts to when pool water has been disturbed while the pool is not supervised. Pool alarms are a great way to know if a child, supervised or unsupervised, or a pet or anyone else accidentally fell into the pool and may need immediate help. With a pool alarm, you should also consider installing locking pool entry systems and gate alarms to create adding protection to your pool and outdoor space.

An assortment of substances and elements that are added to pool water to optimize sanitization, clarity, safety and comfort. Having the proper balance of pool chemicals like chlorine, calcium, algaecides, alkalinity and stabilizers can kill pathogens and bacteria while providing softer, clearer pool water that will not irritate swimmers’ skin or eyes.

A structure installed or constructed around and over a pool to allow for longer, more enjoyable swimming season. Some dome enclosures increase the air and water temperatures while other screen-like enclosures keep bugs away from the swimming area. There are many types of pool enclosure structures including ones built with vinyl or aluminum frames and fully enclosed domes inflated by air pressure from a blower. Fully enclosed domes are the best at preventing pool chemical loss through water evaporation and can even allow for year-round swimming in colder, snow-susceptible climates.

These are the items that make your pool work. From pool pumps and filters to automatic cleaners, pool heaters, and chlorine generators, pool equipment are the pieces that circulate, filter, clean and help sanitize your pool.

A pool heater is the fastest way to generate warmer pool water. Available in natural gas and propane gas, the type of pool heater you use may greatly depend on the type of gas service you have available to your home. A pool heater operates much like the heater in your home by using a relatively efficient combustible (natural gas or propane), but instead of using heat generated from the gas to warm the air, pool heaters generate heat to warm pool water that is circulated via the pool pump and filter system. Pool heaters can greatly extend your swimming pool season, and in some climates, make swimming year-round possible and enjoyable.

The important piece of pool equipment that actually creates the suction power to draw water from your pool, then pushes it through the pool filter and pool heater (if you have one connected), and finally return the cleaned water back to your pool. There are two types of pool pumps, standard and variable speed. Variable speed pumps tend to be more efficient since they will pump slower, smaller amounts of water and then increase power when there is demand for it from the pool filter system.

Pool Putty by A&B, Atlas or Anderson, is a 2-part epoxy putty of resin/hardener, that you mix together to make a variety of pool repairs, for example, to seal up the incoming pump pipe, patch holes or cracks in the skimmer, seal up cracks in pool plaster, or reaffix small pieces of pool tile.

A granular form of chlorine, pool shock  is used to quickly raise the chlorine levels in your pool for a short period of time. Superchlorinating is a term to describe raising the chlorine level 3-5 times the normal amount, for removal of cloudy water, or when chlorine levels drop too low. Shocking a pool is a term reserved for much higher levels, 10-20 times normal levels, to oxidize all organic matter in the pool, kill algae and bacteria, and remove chloramines.

A wide range of games, floats and accessories that promotes fun while in the swimming pool. The most common types of pool toys are fun inflatables like the swan ride-on pool float. Pool toys, usually, are not directly attached to the pool (the exception being some basketball and volleyball sets), and offer challenging and fun ways to enjoy the pool both above the surface and underwater.

A wickedly fun piece of pool equipment that once was only found at parks and commercial pools, but now readily available and relatively inexpensive. Modern pool slides usually have a water element to make the slide even more big park-like, and some slides twist left, right or 360 degrees while others are tall and generate great speeds for a back yard pool.

A handheld, mobile piece of pool equipment used to clean the underwater surfaces of a pool. A pool vacuum can either attach via hose to a pool’s intake and filter system or have its own on-board debris bag or basket.

The balancing of several different pool chemicals at optimal levels to make your pool water clear, clean, safe and comfortable to be in. Using a water test kit is the best way to check if your pool chemistry is optimal, and testing your water at least once a week is crucial to keeping your pool water properly maintained. The wrong pool chemistry can cause a pool owner a lot of extra work and even a lot of money to replace pool equipment due to high or low levels of specific chemicals.

An automatic pool cleaner that attaches to the return side (pressure side) of your pool’s circulation system. Pressure-side cleaners are one of three types of automatic pool cleaners, and they attached to a swimming pool’s return fitting. Water that is pumped via your pool pump or a booster pump from your pool filter back to your pool propels pressure-side pool cleaners around your pool. The water pressure also operates this type of cleaner’s debris removal by using a concentrated stream of water that forces pool debris into the on-board collection bag. Pressure-side cleaners provide efficient cleaning coverage along with dependable automation for easier pool maintenance.

A piece of swimming pool equipment that forces water from the swimming pool through the pool filter, and then back into the pool. Together, the pool pump and filter are known as the filter system – and are “required” equipment for all types of swimming pools and spas, as they maintain fresh sanitary water, and distribute chemicals within the pool.

The main portion of the pool equipment that is in charge of removing small particles and contaminants while circulating fresh pool water. The pool pump draws water from your pool, sending it to the pool filter (which could be a cartridge, sand or DE filter) and then returns the filtered water back to the pool. The system combines both the pump and filter on the same mounting rather than having the pump and filter mounted separately and connected with a length of hose.

A plumbing component of a pool’s pump and filter system, usually a hose, that carries clean pool water away from your pool filter and reintroduces the water back into your pool.

An automatic pool cleaner that operates on electricity and is self-contained meaning it is not connected to the pool’s circulation or filtering system in anyway. Robotic pool cleaners are one of three types of different automatic pool cleaners, and one of the main advantages of a robotic cleaner is not having to run the pool pump and filter to clean your pool’s surfaces. Instead, this type of automatic cleaner uses a low-voltage converter that plugs into an ordinary power outlet to propel the cleaner. Debris and silt is captured in an internal debris bag or basket as the filtered water is expelled back into the pool. In recent years, robotic pool cleaners have evolved with new technologies including GPS navigations, remote controls and multiple cleaning modes and cycles.

A winter cover that uses straps that attach to anchors embedded in the surrounding pool deck to pull the cover taut across the pool instead of laying on the water’s surface. There are two types of safety covers, mesh and solid, and both types are designed to hold the weight of a person if someone accidentally walked onto the pool’s surface while the pool was closed. A mesh safety cover allows for rainwater and snow melt to find its way into the pool water while leaving debris and silt behind so there is no worry about needing a cover pump. A solid safety cover blocks all materials from reaching the pool water which means a cover pump may be needed to remove standing water before the spring opening season. However, a solid safety cover usually leaves your pool water clearer and cleaner since it also blocks dirty water from entering the pool, making your pool opening maintenance a little easier and quicker.

A vast array of pool accessories and equipment designed to protect people, and sometimes pets and animals, in and around the pool. While most pool safety products like pool alarms, pool fences and locking gates and entry systems protect against accidental drowning, there are other accessories like steps, ladders and hand rails that help swimmers get in and out of a pool and protect from injury as well. Other forms of pool safety products include anti-entrapment fixtures that protect swimmers from being trapped on the drain at the bottom of the pool along with pool lift devices and warning signs.

A pool sanitizing system that uses electrolysis and dissolved salt (NaCl) to produce hypochlorous acid and sodium hypochlorite, both common pool sanitizing agents. A salt generator is also known as a chlorine generator, salt chlorinator and salt cell, and it eliminates the need to use pool chlorine to keep pool water clean, clear and safe to swim in. The sanitizing agent produced by a salt generator is just as effective as chlorine but leaves the pool water feeling softer and less irritating to a swimmer’s eyes, skin and hair.

A pool and spa sanitizing system that combines the use of a salt chlorine generator to product chlorine from salt while an ozone generator adds a third oxygen atom to oxygen molecules through an internal electrical process. The created ozone further purifies the sanitized water by oxidizing metals like iron, sulfur and manganese.

A pool chemical designed to kill bacteria and help prevent the growth of algae, viruses and other organic contaminants. Chlorine and bromine are two of the most used pool sanitizers, and they help keep your pool water clean, clear and safe to swim in.

An indicator that pool water is too hard due to a chemical imbalance of high calcium hardness and magnesium levels which leaves mineral deposits on pool surfaces. Scale deposits are easily treated with water balancing chemicals like a metal remover.

Also called a sequestrant, this is a pool chemical with special molecules that bond with metal ions and other suspended particulates in the water to create larger chelate complexes, or large clumps of contaminants. After using a sequestering agent, these large bundles of matter can be captured by your pool filter.

A device attached to the outside of a pool wall with an opening into the pool to allow pool water to steadily flow through. The wall skimmer utilizes an internal basket to catch larger debris like grass blades, bugs, leaves and flower petals while allowing the pool water to flow to the pool filter to remove microscopic particles.

A faceplate or lid that either bolts or snaps on to cover the wall skimmer’s opening. This allows you to winterize and close your pool without draining pool water to a level below the wall skimmer opening and still protect your pool plumbing and filter equipment from freezing, causing damage. The use of a skimmer closure can save thousands of gallons of water a year.

A winter closing accessory used to plug the line running from the bottom of your skimmer to your pool filter. A skimmer guard is usually made of a flexible, but durable, plastic, and is installed into the wall skimmer after the pool’s water level is drained below the skimmer opening. The skimmer plug acts as a combination plug and skimmer bottle to protect skimmer and plumbing from winter ice expansion throughout the winter.

A pool cleaning accessory with a net and rigid frame that attaches to a pool pole. A skimmer net, also called a leaf skimmer, is used to scoop up surface debris and things like leaves that might be suspended in the pool water or on the pool floor.

Also called a solar blanket, a solar cover is a thin, flexible plastic blanket that floats on the surface of a swimming pool for the purpose of warming pool water with the sun’s solar energy. One side of a solar cover is lined with small air pockets that resembles bubble wrap, and these air pockets capture the sun’s energy which is then converted to heat that is transferred to the pool water. Some solar covers can raise a pool’s temperature by up to 15 degrees (F) and help the pool retain that warmth overnight, even if the ambient air temperature drops considerably. A solar blanket also helps protect a pool from losing water through evaporation which limits pool chemical loss, saving pool owners money in several different ways. When a solar cover is not in use, it easily rolls or folds up for storage.

A device that neatly rolls up a solar blanket when swimmers want to use the pool. There are solar cover reel systems for both above ground and inground pools, and most reel systems are manually operated by one or two people turning a crank handle while some reels are electric, battery or solar powered. A solar cover reel makes taking off and putting the solar blanket back on the pool easy and quick and helps protect covers from weather and debris damage.

This is one of the most efficient ways to heat your pool. There are several types of solar heating systems for pools, but the principle for all of them are much the same as they take water from the pool, run it through a series of tubes, panels or other pieces of equipment that uses the sun’s solar energy to heat the water, and then the water is returned to the pool. Heating your pool with solar energy sometimes takes a little longer than gas pool heaters or heat pumps, but there is little or no annual energy costs to run a solar heating system.

Also called a solid winter cover, this is a non-porous cover available for both above ground and inground pools. Solid pool covers prevent rain water, snow melt and other material and debris from entering your pool while it’s closed throughout the winter season. Solid covers are also better at blocking sunlight to help prevent algae blooms when warmer weather arrives and pool chemicals are depleted.

A type of pool chlorine that contains cyanuric acid to act as a sunblock for the chlorine. Sunlight tends to break down chlorine then it burns off, or evaporates, rather quickly, and the cyanuric acid component of stabilized chlorine slows that process down so your pool is sanitized better for longer. Dichlor and trichlor are stabilized chlorines while sodium, lithium and calcium hypochlorites are un-stabilized forms of chlorine.

A common pool chemical used to prevent the loss of chlorine via sunlight in a swimming pool. Pool stabilizer, sometimes referred to as conditioner, usually is cyanuric acid, and it shields chlorine molecules from being destroyed by the sun’s UV rays.

A package of important pool chemicals that are designed to get your pool ready for swimming when it is opened in the spring. A start-up chemical kit usually contains pool shock, clarifier, algaecide, stain and rust removers, and a scale preventer. The pool opening kits usually are pre-measured for several ranges of pool sizes and save pool owners money on chemical costs.

An important element of a pool’s circulation system that uses the power of the pool pump to draw water from the pool, send it through the filtering system to remove microscopic particles. In most pools, the suction port is in the wall skimmer and where a suction side automatic pool cleaner or vacuum connects when cleaning a pool.

An automatic pool cleaner that attaches to the suction side of a pool’s filter and pump system. Suction-side cleaners have an attached vacuum hose that connects to a pool’s suction port that sends pool water to the pool filter for debris and particle removal. One of three types of automatic pool cleaners (the others being pressure side and robotic cleaners), a main advantage to a suction-side pool cleaner is the absence of a debris bag to empty once the pool is cleaned, and they tend to be less expensive, are rather simple to install and easy to operate.

A tool for pool owners to check a variety of chemical levels in their pool. There are many different types of water test kits available from simple strips that dip in water to advanced-technology testers with digital readers. Regardless of its sophistication, all test kits provide useful information regarding levels of important pool chemicals such as chlorine, pH, alkalinity and calcium hardness.

A pool or spa device that can be programmed with custom settings to automatically turn on and off pool pumps and booster pumps. Timers can save pool and spa owners money by running equipment only at the most efficient times but also prevent problems from forgetting to turn the pool pump back on again.

A measure of a pool water’s resistance to change of pH levels. Total alkalinity is the amount of alkali (not alkaline) present in the form of bicarbonates, carbonates and hydroxides in pool water. These levels directly affect and controls a pool’s pH levels. Ideal total alkalinity readings should be between 75 and 120ppm.

Total Chlorine is the sum of combined chlorine and free chlorine, and is a test performed with DPD test kits. Any difference (darkening) between the Free chlorine reading and the Total chlorine reading indicates the presence of Combined chlorine. This requires a shock treatment to remove chloramines, allowing your pool chlorine to work most effectively.

An above ground pool vinyl liner with a bead that resembles an upside down “J,” which is why these liners are also referred to as “J-Hook Liners.” The uni-bead liner hooks over the top of the pool wall and doesn’t require any tracking or coping strip for installation.

A handheld, mobile piece of pool equipment used to clean the underwater surfaces of a pool. A pool vacuum can either attach via hose to a pool’s intake and filter system or have its own on-board debris bag or basket.

A product of mica and other minerals that is mixed with Portland cement to create a solid base or floor for an inground vinyl pool, after the walls are installed. Vermiculite has superb moisture-retentive and insulating properties.

The non-porous pool surface covering that contains the pool water inside the pool. Vinyl pool liners come in a range of sizes, thickness, colors and designs for both above ground and inground pools.

Water balancers help regulate pool water quality or change the chemical balance of a pool when there is an improper level of one or more chemicals. Water balancing chemicals include stabilizers, pH increasers and reducers, calcium hardness increasers, alkalinity increasers and water conditioners.

Typically made of calcium chloride, a calcium hardness increaser works to correct low calcium levels in a pool to help prevent corrosion of pool equipment and to keep the water from etching or staining the pool’s surface.

A tool for pool owners to check a variety of chemical levels in their pool. There are many different types of water test kits available from simple strips that dip in water to advanced-technology testers with digital readers. Regardless of its sophistication, all test kits provide useful information regarding levels of important pool chemicals such as chlorine, pH, alkalinity and calcium hardness.

Durable, vinyl bags that can be filled with water to help secure an inground winter cover. Almost every inground cover has integrated loops that fasten around water tubes to ensure your winter cover will not shift or blow away throughout the winter season.

A protective material that is secure over the top of either an above ground or inground pool for the winter season. Winter cover are either mesh or solid, and both types provide unique benefits of protecting a pool for an extended period of time, including withstanding harsh, rugged winter winds and snow.

Synonymous with the term closing your pool, the purpose of winterizing your pool is to protect your pool equipment, hoses, skimmer and pool surfaces from due to freezing water expansion. Pool winterization also includes having the right pool chemical balance to ensure no algae grows or components and surfaces are etched or start to corrode from too acidic of water.

A sacrificial part made of zinc that is quicker to give up its electrons to counteract galvanic corrosion on metal parts or components in a pool. Anodes are especially popular for protecting pool light niches and metal steps and ladders.