Quick glossary of pool and spa care terms

Trying to untangle the terms can be confusing, we know. To decipher pH vs. PPM and other pool and spa terms, browse this quick glossary. For help with a specific question, you can call our free helpline at 1-800-SOS-POOL (767-7665).

> ACID
A large family of liquid and dry compounds which can reduce the pH of water, usually when the pH level is above 7.6. Importantly, only certain acids are suitable for use in pools. Make sure to read all product labels thoroughly before use.
> ALGAE
Aquatic plants ranging in size from microscopic to giant sea kelp. Generally caused by low levels of chlorine, especially in warm water.
> ALGAECIDE
Chemical(s) that kill or prevent algae from forming.
> ALKALI(s)
A group of compounds that neutralize acids and can increase the pH of water below 7.
> ALKALINITY
The sum of all various alkalis in the water. Total alkalinity test results are expressed as a calcium carbonate equivalent.
> ALKALINITY BOOSTER
Chemical used to raise total alkalinity; often it is sodium bicarbonate.
> BACKWASH
To flush out a filter without disassembling it, a backwash reverses flow of water through filter. Usually used on sand and diatomaceous earth (DE) filters.
> BACTERIA
Microscopic organisms that may be present in inadequately sanitized water; too much bacteria in water may be unhealthy for swimmers.
> BROADCAST
A method of putting granular or powdered chemicals into a pool, by spreading them widely over the surface of the water.
> BROMIDE
Reacts with chlorine in water to generate bromine.
> BROMINE
A powerful sanitizer, algaecide and germicide for use in spas; similar to chlorine.
> CHLORINE
The most widely used chemical for water treatment, with powerful sanitizer, algaecide and germicidal properties. Available as liquid, granules, tablets or powdered compounds which release chlorine in pool water.
> CHLORINE, COMBINED
Also called chloramines; chlorine that is combined with waste matter in pool water that renders the chlorine ineffective to prevent bacteria and algae growth. Usually causes a noticeable chlorine odor and/or eye irritation for swimmers.
> CHLORINE CONDITIONER AND STABILIZER (cyanuric acid or CYA)
Reduces the loss of chlorine from water, due to the effect of sunlight. Reduces chlorine consumption, frequency of application and prolongs chlorine residual.
> CHLORINE, FREE
The most active chlorine in pool water, to prevent bacteria and algae growth.
> CHLORINE, RESIDUAL
A measurement indicating the amount of reserve active chlorine sanitizer in water.
> CHLORINE, TOTAL
The sum of combined chlorine and free chlorine in your pool or spa.
> CHLORINE, UNSTABILIZED
Chlorine that when used in pool water provides fast acting, short-term chlorination; common forms are liquid (sodium hypochlorite) and granular (calcium hypochlorite). A large percentage is lost to the sun's ultraviolet rays. This can be offset by adding 75-100 ppm cyanuric acid or CYA.
> CYANURIC ACID
Also known as pool stabilizer/conditioner. A chemical that helps protect chlorine from the adverse effects of sunlight.
> DIATOMACEOUS EARTH (DE)
Commonly used in filters; also known as DE and filter aid.
> FILTER(s)
Types of pool and spa filters include diatomaceous earth (DE), cartridge and sand filters.
> NITROGEN
Interferes with chlorine by forming chloramines. Enters pool water from leaves, sweat, urine and fertilizers.
> NON-CHLORINE SHOCK
A persulfate compound with active oxygen that helps break down oily substances. With non-chlorine shock products, you usually can use the pool or spa 15 minutes after applying. An important note: Non-chlorine shock does not disinfect water or kill algae.
> PARTS PER MILLION; ppm
The measurement for chlorine, total alkalinity, hardness and cyanuric acid (stabilizer/conditioner) in water
> pH
On a scale of 0 to 14, the measurement of the degree of acidity (below 7) or alkalinity (above 8) of water. The best range for swimming and spa water is 7.2 to 7.6.
> pH BOUNCE
A condition when pH is unstable; it usually indicates a need to correct total alkalinity of the water before making any other corrections.
> PHOSPHATES
Byproducts of organics that enter pool water which algae feed on.
> PUMP
Used to circulate the pool water through filters, heaters, feeders, vacuums and pool sweeps.
> SANITIZING/DISINFECTION
The use of germicides such as chlorine and bromine to prevent illness and/or irritations which may occur due to swimming in untreated pools and spas.
> SCALE
A rough, unsightly, stony deposit of hard water minerals on the walls or in the filter, heater and piping of a pool. Scales can drastically reduce filter or heater efficiency and frequently causes heaters to burn out. To avoid scale, keep pH level between 7.2 and 7.6 and monitor the use of calcium-based chlorine.
> SHOCK (SUPER CHLORINATION)
The practice of using chlorine to produce 5-10 parts per million (ppm) reading. Used regularly in season to control chlorine resistant elements and as needed to kill existing algae. To assist removal by the filter, the use of a water clarifier is recommended. NOTE: Do not swim or sit in water with a chlorine reading above 3 ppm.
> SKIMMER
Strainer(s) at the top or bottom point(s) of a pool, to screen out leaves or other debris. Skimmers also are used to operate vacuums and some type of pool sweeps.
> SODA ASH
A chemical used to raise pH; also called sodium carbonate; included in Kem-Tek pH Plus products.