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Acid- A PH that is below neutral. This PH is below 7.

Acid Demand- A test used in pools to determine the amount of acid that needs to be added to reach the correct level.

Acid Wash- Referred to as drain and clean. Stripping a thin layer of plaster off the pool so a new layer will be exposed. This is done when there is a great deal of algae covering the pool.

Aeration- Mixing air and water together.

Air Bleeder Assembly- The bleeder is on the top of the filter, and is used to release air that has become trapped in the filter. Also referred to as the air relief valve.

Algae- A water plant that is known to have more than 20,000 species of it. It usually forms at the surface of a pool, and is usually green in color. However, it is also known to be yellow, black, or blue-green.

Algaecide- Chemical that not only kills, but prevents algae.

Algaestat- A chemical that prevents algae from growing.

Alkaline- A PH above neutral. This PH is above 7. Also known as a base, it will dissolve in water.

Alkalinity- In water, this the the amount of bicarbonates and carbonates. It is measured as parts per million.

Aluminum- A natural forming mineral in pool water.

Aluminum Sulfate- A product that attracts and sinks everything to the bottom of the pool. Once all the materials are at the bottom of the pool, the pool may be vacuumed. This is commonly known as Alum.

Ammonia- NH3. A compound that contains nitrogen. It is combined with chlorine to produce chloramines.

Anion- A negatively charged ion that is attracted to anodes in electrolysis.

Automatic Pool Cleaner- A device that will vacuum the walls and floor of the pool and remove debris.

Available Chlorine- A rating used to rate the strength of chlorine products.


Backfill- Moving the soil back after a pool has successfully been installed.

Bacteria- Organisms that break down organic matter. Some may cause diseases that are infectious.

Backwash- Cleaning the filter elements by reversing the flow of the water.

Balance- Properties of water are at an ideal range, and will not allow anything to corrode.

Balanced Water- All chemical parameters balance each other and are where they should be.

Ball Valve- A valve that is used to increase or decrease water flow.

Base- A PH level above 7. Common bases for pools include Sodium Carbonate, Soda Ash,and Sodium Bicarbonate.

Base Demand- A test used to determine how much more base is needed for the correct amounts.

Biguanide- A non-chlorine sanitizer. It gives the water a smooth feeling to it. It can not be combined with chlorine, bromine, or any mineral sanitizers.

Blower- A device that produces bubbles in a spa, hot tub or whirl pool.

Blue Fingernails- Too much copper is in the pool water, thus resulting in blue fingernails.

Booster Pump- A pump that may be used to power an automatic pool cleaner. Also used to maintain pressure or or flow or to increase them.

Borate- An element that is used for cleaner water.

Breakpoint Chlorination- A pool that has been shocked and oxidized. This will reach a level of chlorine that will allow molecular bonds to break apart.

Bromine-A sanitizer that is not stable in the sunlight. Good for higher PH levels. Great for hot tubs.

BTU- British thermal units.

Buffer- Chemicals that prevent fluctuation in PH.

Buffering Capacity- Resisting changes in the PH in the pool. This prevents water balance.

Bypass- Pipes, gates and valves that redirects water flow around a piece of equipment.


Calcium- A soft alkaline earth metal that is gray in color.

Calcium Carbonate- CaCO3. Compounds that are formed on a pool surface when calcium hardness levels are too high.

Calcium Chloride- CaC12. A white salt that is used to raise the calcium hardness level.

Calcium Hardness- Calcium content of water.

Capacity- The total number in gallons that a swimming pool contains.

Capacitor- The pool motor’s battery.

Cartridge- An element in some filters that is replaceable. It is porous.

Cation- A positively charged ion that is attracted to cathodes.

Centrifugal Pump- a pump that creates pressure in the water by velocity that is from the centrifugal force.

Check Valve-The device that is located in a pipe that allows water to flow. Water will only flow in one direction with this valve.

Chelator- A water soluble material that bonds well with metal ions. These bonds will help to keep stains from depositing on pool surfaces and any equipment.

Chelated Copper- Copper algaecides with ingredients that prevent copper from staining a pool surface or making the water turn a different color.

Chemical Feeder- A mechanism that adds chemicals into a pool at a predetermined rate. This can be used for either chlorine or bromine, or using PH adjusting chemicals.

Chloramines- Substance made when chlorine combines with waste, such as nitrogen or ammonia. It will cause odor and irritation to the skin and eyes.

Chlorinator- An electrical device that add chlorine to the pool automatically.

Chlorine- A gas that is added to a pool that will act as an oxidizer and sanitizer.

Chlorine Demand-the amount of chlorine that is removed when sanitizing the pool.

Chlorine Enhancer- A compound used to make chlorine work harder.

Chlorine Generator- A generator that supplies its own supply of chlorine, as well as hypochlorus acid or hypochlorite.

Chlorine Neutralizer-A chemical that is added to a pool to make chlorine not harmful. It will counteract the bleaching effect in bromine and chlorine. High levels will not effect swimmers if this is added to a pool or spa.

Chlorine Residual- Chlorine that is ready to sanitize a swimming pool. Also referred to as Free Available Chlorine.

Clarifier- A compound that is used to coagulate particles to be removed by a filtration system.

Coagulant- A chemical compound that is added to water that gathers particles for filtration.

Coping-The cap on a pool that has a finished edge. Can also be the portion of the pool that secures the vinyl liner to the pool wall.

Conditioner- Also referred to as a stabilizer, this is a chemical that makes a shield from the sun around the chlorine molecules.

Contaminants- Any substance that will reduce water clarity. They may present a health hazard.

Corrosion- A chemical imbalance or low PH that is caused by destructive erosion of the surface of the water.


Decks- An area that is agent to a pool, hot tub or spa. Used for swimmers to lounge, sit and relax.

Defoamer- A chemical that is added to the water to destroy foam. Also known as anti foam.

Diatomaceous Earth: A white powder that is added to the skimmer when the pump is on. This powder then deposits on the grid and become a filter medium.

Dichloro-S-Triazinetrione- An oxidizer that is a chemical compound. Used to make cleaning agents, bacteriocide, and algicide. Forms hypochlous acid.

Disinfect- The killing of any pathogenic organisms that cause disease.

Diverter Valve- Valve used to manipulate the drain and skimmer to the pump.

Diving Board- A way to enter a pool. Consists of semi rigid board that has a fulcrum mounted below it to give spring to a swimmer jumping in.

DPD- An indicator reagent that is used to measure the free chlorine available, bromine, total chlorine, ozone and other oxidizers that are in the pool water.

DPD #1- A test table that is used to measure free chlorine available amounts or bromine that is in the water.

Drain- Plumbing feature that is installed on the suction side of the pump in a pool. Located in the deepest portion of the pool.

Dry Acid- Used to lower the PH and total alkalinity of the pool. Safer to handle than a liquid acid.


Efficacy- Producing an effect. An example is that chlorine has the efficacy that is effected by the sun and other factors.

Effluent- Any water that flows out of the pump, heater or filter. Also known as pressure side.

Elbow- A fitting used in plumbing that has a 90 degree angle or a 45 degree angle. Will be made out of PVC pipe or metal, and occasionally made of plastic.

Electrolysis- An electrochemical reaction that is made from two metals being plumbed together or if there is an improper grounding of pool equipment.

Enzymes- Used to break down oils in swimming pool formulations.

EPA- Stands for Environmental Protection Agency. This is a federal program.

Equilibrate- To bring a chemical balance to a pool or spa.

Etching- Corrosion on the surface of the water. This is caused by water that is acidic or has a low calcium hardness or total alkalinity that is low.


Fiberglass- Filaments of glass that are spun and hardened to be used for pool shells and hot tubs.

Fill Water- Water that is used for filling or adding more to the pool.

Film X- A citric acid compound that is used for the cleaning of plaster.

Filter- A device that catches and removes particles from a swimming pool.

Filter Cartridge- An element composed of paper or polyester that is used as a filter medium in pools with filters.

Filter Cycle- The amount of time that the filter operates between cleanings.

Filter Element- A device that removes suspended debris from the water.

Filter Rock- Rounded rock or gravel that is used for supporting sand in sand filters.

Filtration Rate- The speed measured at which the water is flowing through the filter.

Fireman’s Switch- A switch inside the time clock that shuts off the heater 10 to 15 minutes before shutting off the water circulation pump. This will allow less lime buildup in the heater exchange.

Flocculent- A chemical that is used to suspend particles in a pool. It will then settle to the bottom of the pool so it can be vacuumed.

Flow Meter- A device that measures how many gallons per minute of water are flowing through a recirculation system.

Flow Rate- The volume of water that has flowed past a point during a specific measure of time.

Foaming- Surface foam that is on top of water, such as in hot tubs. It forms when there are high TDS levels that combine with soft water and oils. Comes from soaps used, oils, body lotions, suntan lotions, deodorants, hairsprays, etc.

Free Chlorine Available- Chlorine that has not combined with anything in the water already.


Gate Valve- A valve that is opened by moving the gate or wedge out of the path of the fluid. Turn it lefty loosey, righty tighty.

Gasket- A seal that fills in the space between two objects.

Gas Valve-A valve located in the pool heater that directs gas to the pilot and the burner tray from the meter.

Gelcoat- A surface that is colored of a fiberglass pool or spa shell. Will harden to a durable form that is smooth.

GFCI- Stands for Grounded Fault Circuit Interrupters. Required by the National Electric Code for home electrical wiring.

GPD- Gallons per day.

GPH- Gallons per hour.

GPM- Gallons per minute.

Grab Rail- A hand rail that is either plastic or steel that is used by swimmers for gripping to steady themselves.

Green Hair- A condition that results in green hair tint when there is too much copper in the pool water.

Grout- A mortar that is used to fill cracks.

Gunite- Concrete and sand mixed that are sprayed onto a steel form that make a swimming pool shell. Once this process if done, paint or other finishes may be added to this to finish it out. This is applied using a pressure hose.


Halogen- A chemical element that contains chlorine, fluorine, bromine, iodine and astatine.

Hand Skimmer- A net that is used to remove floating objects in the pool such as leaves and bugs. It is attached to a long pole.

Hard water- Water with mineral salts. This water does not lather very well. It also forms scale.

Hardness- The amount of calcium and magnesium that is dissolved in water.

Hazmat- A hazardous material. It can be either a gas, liquid, or solid. It may be explosive, toxic, flammable, corrosive, radioactive, or explosive.

Heater- Mechanism that will heat the water.

Heater Elements- The device that creates and transfers heat to the water. This is located inside the heater housing.

Heater Exchanger- A set of copper tubes that absorb heat. The heat is below the copper tubes and then transferred to water that is cycling through the tubes.

Heater Housing- A unit that facilitates water movement by and through the heater element.

Herbicide- A chemical that is used to kill or control algae and plant growth.

Hertz- HZ. A measurement of a frequency of alternating currents.

Hot Tub- A wooden tub filled with hot water that is circulating.

Hydrochloric Acid- A strong acid that is used in pools to lower PH levels. It may also be used to clean a pool that has been emptied.

Hydrogen Ion- A positively charged nucleus of a hydrogen atom that will increase the levels of hydrogen ions in the water. This will cause it to lower the PH. Also known as H+.

Hydrogen Peroxide- An oxidizing agent used in pools. It is colorless, and is commonly found in homes as an antiseptic.

Hydromassage- A massage using pressurized water.

Hydrostatic Pressure- Built up water that creates a pressure beneath a pool shell.

Hydrostatic Relief Valve- A fitting that is placed in the floor of the pool that automatically releases pressure from beneath the pool.

Hydrotherapy Jets- A spa feature that allows water and air to be blended creating a stream of water that is enriched with air.

Hyprobromous Acid- Bromine that is active in the pool water.


Impeller- The rotating unit of a pump.

Incoloy- A metal alloy that is used for making heater element sheaths.

Influent- Water that enters the pump or filter.

Inlet- A fitting on the water return line.

Ionizer- A sanitation device that does not remove any waste.

Iron- Water should be tested with an iron testing kit. Iron can make the water brown or green. Some irons may stain a pool surface.

Isocyanurates- A group of chlorine sanitizes that has a stabilizer that will protect the chlorine from the UV rays of the sun.

J Jacuzzi- A brand name for a spa or hot tub.

Jandy Valve- A three way valve. A brand name of a valve.

Jet- An outlet that is used to project a high stream of water.

Jet Pump- A pump that is used for hydrotherapy jets.


Kilowatt- A measurement of power that is equal to 1000 watts.

Kilowatt Hour- The measurement of power that is exerted of one kilowatt in one hour


Ladder- A structure located in the pool for climbing in and out of the pool.

Ladder Bumpers- Rubber caps that protect the plaster on the pool from the ladder.

Laminating- Layering and bonding materials together for greater strength, better sound absorption and a lower heat transfer.

Langelier Saturation Index- Used to determine water balances according to the PH levels in the pool with the total alkalinity, water temperature and calcium hardness. When all elements are in balance, the water will not be corrosive or scaling.

Laterals- Capped nipples found at the bottom of a sand filter. Sand stays in the filter tank but water is allowed to pass through.

Leaf Net- See Hand Skimmer.

Leaching- A process of taking minerals from plastic interiors. May also take tanic acid from wooden hot tubs.

Ligand- An ion, molecule, or atom that gives one or more of its electrons through a bond.

Liner- A container that holds water in pools. May also be called a vinyl liner.

Liquid Acid- Used for acid washing, as well as lowering the PH levels and total alkalinity.

Liquid Chlorine- Commonly known at bleach. Added to water to be a disinfectant.

Light Niche- The area in the pool where the light fixture is.

Lithium Hypochlorite- A sanitizer that is used often in hot tubs. Can work in higher temperatures. Has a longer shelf live and comes in a dust form.

Low Water Suction- An alternative that is cheaper than a main drain. It is low on the wall in the deep end.


Magnesium- A mineral that can lead to stains and scale.

Magnesium Hardness- The amount of magnesium that is dissolved in water. If levels are too high scale will be formed.

Main Drain- Located in the deepest part of the pool, it is also referred to as the drain.

Make-up water- Water that is used to replace the water lost from evaporation, splash out, or leaks. Also known as tap, source or refill water.

Marbelite- Also called plaster. Mixture of white marble dust and white cement that is used over the gunite in a pool. Also called marcite.

Mechanical Seal- A seal that is located behind the impeller which will prevent water from running out along the pump seal.

Mineral- They may cause scale or stains. Best known minerals include copper, calcium, silver, zinc, nickel, aluminum, cobalt and magnesium.

Micron- Unit of length that is equal to one millionth of a metre. Used to measure pore size of filter media in pools.

Multiport Valve- A 6 way valve. The handle of the valve can be turned to perform various functions. Water can be sent to waste, be used for rising the filter, used for backwashing, turned so all valves are closed, used to filter normally, or bypass the filter to have maximum circulation.

Muriatic Acid- A very strong acid that is used to lower the PH levels or total alkalinity in a pool.


Nascent Oxygen- One oxygen atom that has not bonded to anything.

Neutralizer- A chemical that is added to bromine or chlorine that will make it harmless.

Nitrogen- A gas that causes chlorine to disable.

Non-chlorine Shock- Chemical compounds that are used to shock a pool to destroy swimmers waste, ammonia, or nitrogen.

Noryl- Brand name for a resin that is used for various pool fittings.


Organic- Oxidation- A process that removes compounds not wanted in the pool water.

Organic Matter- Urine, suntan lotion, sweat, dead skin, cosmetics, lotions, leaves, and other debris found in water left by swimmers and nature. Also known as organic waste or bather waste.

O-ring- A loop of elastomer that is used as a seal or a gasket.

ORP- Stands for Oxidation Reduction Potential. Measurement of the oxidizers ability to oxidize any contaminants versus the contaminants ability to oxidize the oxidizer.

OTO- A way to test for free available chlorine levels.

Oxidation- Destruction of organic waste in water.

Ozonator- A device that produces ozone in water that is also a sanitizer.


Pathogen- Pathogenic organism. An organism that can cause an illness and even death.

PH- A measurement of how much acidity there is in water. Neutral has a pH of 7. Anything below is considered to be acidic while anything above 7 is considered to be basic or alkaline.

Phenol Red- The dye used to test PH. Found in liquid test kits. Reads ranges from 6.8 to 8.4.

Photometer- An instrument that is used for testing water conditions.

Pink Slime- Algae that shows up in hot tubs. Pink Slime is usually diminished if biguanide is used.

Plaster- See marbelite.

Plumber’s Snake- A tool used by plumbers. It is a flexible auger that removes clogs that can not be removed by a plunger. Also referred to as a toilet jack.

Polyethylene- A plastic that some hot tubs are made of.

Polymer- An algacide that is made up of repeating polymer molecules.

Potassium Carbonate- A PH increaser.

Potassium Monopersulfate- A shocking compound that is oxygen based. It is fast dissolving and used in hot tubs. Shocking the hot tub with this, and the consumer can use the hot tub in 15 minutes.

PPM- Parts per million.

Precipitate- A solid that is forced out of the solution and then forms either flakes or a haze.

Pressure Check- Test for the rate of water flow.

Pressure Gauge- A device that provides how much a system is operating and how much pressure there is in a filter.

Pressure Side- Return side of the plumbing.

Pressure Switch- The switch used in pool heaters that prevents it from firing.

Priming- Starting a water flow to the pump so it does not suck any air.

PSI- Pounds per square inch.

Pump- A device that causes hydraulic flow and pressure for the pool water to be circulated.

Pump Capacity- The amount of water that a pump is able to move in a specific time period.

Pump Curve- A chart that shows the water flow at a given resistance.

Pump Strainer Basket- A device used on the suction side of the pump that traps large debris from the pool.

PVC- Polyvinyl chloride used to make PVC pipes for plumbing.


Quaternary Ammonium Compounds- Algacide made of ammonia compounds. Also known as quats or QAC.


Rate of Flow- The amount of water, expressed in GPM, that flows past a point in a given amount of time.

Reagent- Chemical indicators that are used to test swimming pool water. Usually small tablets or a bottle that come with the testing kit itself.

Re-bar- A bar that is used to add strength to concentrate. Stands for reinforcement bar.

Redox Potential- Abbreviation for reduction oxidation potential. See above under ORP.

Relay- In a spa’s electrical circuit, this is what controls the power to another device.

Residual Bromine- The amount of free available bromine in the water after the bromine levels have been satisfied.

Residual Chlorine- The amount of free available chlorine in the water after the chlorine levels have been satisfied.

Restricted Flow- Flow of water that is not moving at its full potential. Something is blocking the flow of the water.

Return Inlet- A fitting that allows water to return to the spa from the circulating pump.

Roto-Molding- A rotational molding process for spas.

R-Value- A measurement of resistance to the flow of the heat. A higher R value will mean better energy costs.


Sand Filter- A tank made from fiberglass or ABS plastic that is filled with sand and gravel. Water if forced through the sand and gravel to the bottom of the tank.

Sanitizer- Chemicals that remove contaminants in the pool water.

Saturation Index- An index that tells whether water is forming scale or is corrosive. PH, total alkalinity, calcium hardness, and water temperature all factor into the index. Ideal range should range from -.3 to +.3.

Scale- Mineral deposits left on a pool surface.

Scum- Foreign matter that rises to the surface of water. A layer or film is produced.

Scum Digester- An enzyme product designed to break down oils soap film or lotion film in spa water.

Seating Capacity- The total amount of seats in a hot tub.

Sediment- Solid material that has been settled out of the water.

Sequestering Agent- A material that prevents and removes stains from metals in a pool.

Silt- Very small soil particles. They measure in between .004 and .062 mm. They may be too small to be trapped into the circulation system, so a clarifier may be needed.

Silver Ions- Used to sanitize water so less chlorine can be used. Disinfects that water so that bacteria is not produced.

Simazine- Used for killing black algae, this is a chemical that is used in spas and swimming pools.

Skimmer- Plumbing fitting that is on the suction side of the circulatory system in the pool.

Skimmer Basket- A basket that is located under the skimmer lid. Used for straining any debris caught.

Skimmer Gutter- An overflow channel that is located at the edge of the pool that is commonly known as a gutter.

Skimmer Net- Leaf rake that has been attached to a pole to skim the pool and remove any debris.

Shock- Pool sanitizer that removes unwanted waste from the pool. The levels are brought up high so that the breakpoint can be reached, in order to fully sanitize the pool.

Slurry- Water with a high concentration of suspended solids.

Soda Ash- A base that raises the PH level of a swimming pool. Also known as sodium carbonate (Na2CO3).

Sodium Carbonate- Commonly known as baking soda. This is a base used to raise the alkalinity in a pool.

Sodium Bicarbonate- NaHCO3. Added to water to increase the total alkalinity.

Sodium Bisulfate- Granular form of acid that is used to counteract scaling conditions in a pool.

Sodium Dichlor- Pool sanitizer used for shocking a pool.

Sodium Hypochlorite- Liquid Chlorine.

Sodium Tetraborate- Used to prevent and remove algae. Algae can not produce carbon dioxide when sodium tetraborate is used.

Sodium Thiosulfate- A chemical that is used to either neutralize or de-chlorinate pool or spa water.

Soft Water- Water with low levels of magnesium or calcium.

Solar Cover- A floating cover that increases temperature in a pool since it absorbs the sun’s radiation.

Spa- A small tub that is filled with filtered hot water. Has hydrotherapy jets.

Stabilized Chlorine- A compound that is made of chlorine and cyanuric acid.

Stainer Basket- A basket that is located at the pump with small holes that prevent the pump impeller from clogging.

Stainless Steel- A material that will not rust and resists stains.

Superchlrorination- Also known as shock treatments. Elevating the free chlorine available another 5 ppm. Usually adding 7 to 10 times the amount of normal chlorine to kill bacteria.


Telepole- A pole that extends in length that is used for cleaning a pool.

Test Kit- A device used to measure chemical levels in a pool. Kits contain vials, titrants, reagents, and color comparators.

Test Strips- Plastic strips with pads that have reagents on them to test the pool water.

Time Clock- A device that turns a pump or pool cleaner on or off at a scheduled time.

Titration- Method to test total alkalinity, acid/base demand, and calcium hardness. A drop of titrant is added until there is a change in the color.

Total Alkalinity- Total amount of alkaline material in the pool water.

Total Chlorine- The amount of chlorine that is in a swimming pool.

Total Dissolved Solids- A measure of everything that is dissolved in the pool water. Also referred to as TDS. To lower the TDS, the pool water must be partially drained and then refilled.

Trichlor- A slow dissolving chemical compound that has a PH of 2.9. It prevents chlorine from being destroyed by the sun’s UV rays.

Trowel- A tool that is used most commonly on pool decks. It is used for applying coatings to concrete.

Turnover Rate- The time in hours that the pump needs to circulate water in the pool.


Ultra Violet Light- An invisible frequency of light that is emitted by the sun. It can cause substances to glow and also form chemical reactions.

Ultra Violet Light Treatments- Using UV light radiation to destroy contaminants in water.

Underdrain- The lower portion in swimming pool filter. Filtered water is directed back into the pool through this.

Underwater light- A light that is below the surface of the water to light the pool.

Urethane Foam- A plastic material that insulates that is used to reinforce the shell of the hot tub. It will also add support and slow heat loss.


Vacuum- A cleaning process for the swimming pool. Includes suctioning leaves and other debris from the floor of the pool. Algae is also swept up.

Valves- Used to adjust the water flow when dealing with hydraulics. Water may be obstructed or restricted. Water may also only flow in one direction.

Vermiculite- A mineral that expands when applied to with heat.

Venturi- Restricting pipe size in order to create more water velocity.

Vinyl Liner- A container that holds water in one type of pool. May also be just called a liner.

Virus- A pathogen that can cause disease.

Volute- On a pump, this is the casing that receives fluid that is being pumped by the impeller. This slows down the rate of flow for fluids.


Waste Gutter- In a pool that has 2 gutters, this is the outer chamber. This outer gutter collects rain water and wash water and diverts it to waste so it can enter the pool.

Water Balance- The condition of the water, taking all measures into account. Water will be neither corrosive nor scale forming.

Water Volume- The amount of water in a pool or spa.

Water Clarifier- See above Flocculant.

Weir- Small door that floats on the skimmer. It prevents debris from floating back into the pool if the pump is shut off.


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Zeolite- Used in sand filters as an alternative to quartz or silica. It is able to absorb heavy metals such as iron, and absorbs ammonia and nitrogen compounds. When used, it can reduce backwashing by up to 50%.

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