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Surrey Branch


Pool & Spa Terms

At Imperial Paddock Pools, educating pool and spa owners has been one of our main initiatives since we built our first pool all the way back in 1951. Residential and commercial pool owners all the way from Bowen Island to Belcarra, Maple Ridge, Langley and White Rock count on the Imperial team for knowledgeable, professional pool and spa care.

Browse the glossary below to learn more about common pool and spa care terms.

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Air-Relief Valve

This is a manually operated valve that is usually made of brass or plastic and found at the top of a filter tank. It relieves pressure inside the filter and removes air from within (this is called filter bleeding). It is sometimes called a pressure-relief valve.


These microscopic, plant-like organisms are commonly found in pools and they contain chlorophyll. Algae growth is facilitated by carbon dioxide and the organisms use sunlight to achieve photosynthesis. Algae are introduced into pools by rain or wind and grow in colonies, usually producing bothersome masses. Algae do not cause disease but it can include bacteria and be slippery to the touch. Scientists have identified more than 21,000 known species of algae. The most common types pool and spa owners will encounter are black, blue-green, green and mustard coloured. Pink and red algae-like organisms can be found in nature but these are bacteria clusters, not true algae growth. By keeping your pool sanitary and by shocking it and using superchlorine, you can help hinder the growth of algae.


These are products that stop or stabilize the growth of algae in pools and spas.

Automatic Pool Cleaner

This is a pool maintenance system that removes debris from the pool’s interior automatically.


Backflow is the backing up of water through a pipe. During a backflow, water travels opposite of its intended direction.


This is the thorough cleaning of a filter by reversing the way water flows through it. It causes dirt and rise water going to waste.

These are microscopic organisms. Some bacteria can pose health dangers to swimmers.

Balanced Water

Pool and spa owners achieve water balance by finding the right ratio of mineral content and pH levels. Balanced water is not corrosive and does not form scale.

This is a common term for a bromide salt that pool and spa owners use to supply bromide ions to the water so they may be oxidized or changed into hypobromous acid, a form of bromine. It is commonly administered as a disinfectant.

This is a common name for a chemical compound that contains bromine. It is used as a disinfectant to destroy bacteria and algae growing in pools and spas. Bromine is available in tablet form or as sodium bromide, a granular salt.

This is the commonly used abbreviation for British Thermal Unit. This is the amount of heat necessary to raise one pound of water one degree Fahrenheit.

Calcium Hardness

Calcium hardness indicates the amount of dissolved calcium in your water. The ideal range is between 175-225 PPM, depending on your pool or spa’s surface type.

Centrifugal Pump
This is a pump that includes an impeller that if placed on a rotator shaft and enclosed in a casing or volute that has an inlet and a discharge connection. The rotating impeller creates pressure in the water by the velocity from the centrifugal force.

Check Valve
This mechanical pipe allows water to flow on air in one direction.

Chemical Feeder
A chemical feeder is any type of device that dispenses chemicals into your residential or commercial pool or spa at a rate determined by the user. Some chemical feeders distribute chlorine or bromine while others administer chemicals that can adjust the pH level.

These irritants are formed by a combination of nitrogenous compounds and free chlorine. Nitrogenous compounds are introduced into pool or spa water through urine, perspiration, cosmetics, sun tan oils and other sources.

This is a device that dispenses chlorine and other compounds into pool water in a controlled, gradual manner.

This term is widely used to describe any type of chlorine product that is used as a disinfectant in swimming pools to kill or control bacteria and algae. Chlorine oxidizes ammonia and nitrogen compounds (swimmer waste).

Chlorine Demand
This term refers to the amount of chlorine you need to add before a free chlorine residual can be maintained.

Chlorine Generator
This device transforms sale (sodium chloride) into free chlorine (hypochlorous acid) through electrolysis.

Chlorine Neutralizer

This is a chemical that renders chlorine harmless. It is often used in test kits to offset the bleaching power of chlorine and bromide in order to make pool water tests more accurate. It is sold as chlorine and bromine neutralizer, it is used to destroy excessive amounts of these chemicals so that high levels will not harm swimmers.

Chlorine Residual
This term refers to the amount of chlorine left to battle new bacteria that enter the pool. It can also refer to the amount of chlorine still in your system after chlorine demand has been satisfied.

Combined Chlorine (Chloramine)
These area chlorine-ammonia compounds that can cause chlorine odour and eye irritation. Experts do not recommend using this because it is a poor sanitizer of pool water.

The coping is the cap or top lip on the pool or spa wall that completed the finished edge around the pool or spa. It can be formed, cast in place or pre-cast and even pre-fabricated of extruded aluminum or rigid vinyl. It may also be part of the system that secures a vinyl liner to the top of the pool wall.

This term refers to the slow breaking down of pool or spa equipment by etching, pitting or dissolution. It is caused by improper water balance, misuse of acid or acidic products or even from soft water.

Cover, Hard Top
This is a cover used on pools, spas and hot tubs that rests on the lip (coping) of the pool or spa deck. It is not a floating pool cover. It is used as a barrier to swimmers and bathers as well as for maintenance and thermal protection of the pool and its water.


A diffuser is a porous plate, tube or other device through which air is forced and then divided into small bubbles for water diffusion. A diffuser can also be an overdrain or even a sand filter. Pool and spa owners also use diffusers on closed-fact impellers on pumps to concentrate waterflow to the center of the impeller.

Diverter Valve

This is a plumbing fitting used to change the direction of the flow of water. Some diverter valves are used on pool/spa combination units to allow the use of the spa and then switch the flow back to the pool.

A drain is a plumbing fitting that is installed on the suction side of the pool, spa or hot tub pump. It is sometimes referred to as the main drain and is found in the deepest part of the pool. It is not the same kind of drain found in kitchen sinks. Main drains do not permit the water to drain to waste, rather they connect to the pump to boost circulation and filtration.

Dry Acid

This product lowers pH levels and total alkalinity. Many pool and spa owners prefer dry acid over muriatic acid due to many handling, storage and safety concerns.


This is a device that removes undissolved or suspended particles from pool and spa water by redirecting the water through a porous substance (a filter or other element). The three main types of filters used in pools and spas are sand filters, cartridge filters and diatomaceous earth systems.

Filtration Rate

This term refers to the rate at which the water travels through a pool or spa filter. It is expressed in US gallons per minute (gpm) per square foot of filter area.

Flow Rate
This term applies to the quantity of water flowing past a designated point within a specified time, such as the number of gallons flowing past a point in one minute. It is referred to in terms of gpm.

Free (Available) Chlorine
This is chlorine in a form that is capable of destroying algae and bacteria. Its preferred range for pools and spas in Vancouver is 1.0 to 3.0 ppm.


This is a mixture of cement and sand sprayed onto contoured and supported surfaces to construct a pool or spa. Gunite is mixed and pumped to the site in a dry form and water is added later at the point of application. Pool construction teams usually apply plaster on top of the gunite.

A pool gutter is an overflow trough located at the edge of your pool. Floating debris, oil and other elements that are lighter than water flow through the gutter. More often than not, pools that feature gutters do not have skimmers.

Hand Skimmer

A hand skimmer is a screen that has been affixed to a frame and attached to a pole. It is used to remove large floating debris, including leaves, twigs, insects and other pollutants, from the surface of your pool or spa.

Heat Exchanger
This is a device that is located within a pool or spa heater. It allows the transfer of heat from its source to the water itself. A heat cylinder usually contains several metallic tubes with fins located just above the flames.


A fossil-fueled, electric or solar device, a pool heater raises the temperature of your pool, spa or hot tub.


Pool and spa owners also refer to this item as a vinyl liner. It refers to the membrane that acts as a container to hold or contain water.

Main Drain

The term main drain usually refers to any plumbing fitting that is installed on the suction side of a pool, spa or hot tub pump. It is located in the deepest section of your home or business’s pool. It works differently than drains found in kitchens. Main drains do not allow the water to drain to waste, instead they help boost circulation and filtration.


This is a chemical that is used to make chlorine or bromine harmless for swimmers. Neutralizers remove excessive amounts of chlorine from pool and spa water.


This is a shocking compound that does not include chlorine. It removes or destroys contaminants and chloramarines in pool water without raising the level of chlorine when superchlorinating.

Personal Flotation Device (PFD)

This term refers to anything a swimmer uses to stay afloat in the water.

Parts per Million (PPM)
This is a measurement for chemical concentration.

pH-Potential Hydrogen
Indicates the level of acidity or alkalinity of water on a scale ranging from 0-15. A low pH causes etched plaster, metal corrosion and eye irritation. A high pH causes scale formation, chlorine inefficiency and eye irritation. The ideal range for pH in swimming pools is 7.4 to 7.6.

This is a mechanical device, usually powered by an electric motor, which causes hydraulic flow and pressure for the purpose of filtration, heating and circulation of pool and spa water. Typically, a centrifugal pump is used for pools, spas and hot tubs.

Pump Capacity
This term refers to the amount of liquid a pump is able to move during a pre-determined timeframe. This output is measured in gallons per minute.

Pump Curve
This is also sometimes called a pump performance curve. This is a graph that represents a pump’s water flow capacity at any given resistance.

Pump Strainer Basket
This term refers to a device placed on the suction side of a pump. It contains a removable strainer basket designed to trap debris in the water without causing much or any flow restriction. Sometimes, people call this a "hair and lint trap."


These are tablets, powders or liquid material that are used in water testing.

Saturation Index

Saturation index refers to a value based on water temperature, total alkalinity, calcium hardness and pH levels. The saturation index predicts the tendency of pool water to be corrosive, neutral or able to form scale.

This refers to coarse deposits of calcium on swimming pool walls, floors and plumbing equipment.

Shock Treatment
A practice that involves adding large amounts of oxidizing chemicals (usually non-chlorine oxidizers, such as sodium persulfate or potassium peroxymonosulfate) to the water in order to destroy ammonia and nitrogen compounds as well as waste products from swimmers.

Skimmer Basket
This is a removable, slotted basket/strainer that is placed on a skimmer. It is designed to trap floating debris without causing waterflow restriction.

Solar Cover
A solar cover increases the water temperature by absorbing and transmitting solar radiation. It reduces evaporation and prevents windborne debris from entering the water.

Stabilized Chlorinating Products
This is a form of chlorine that is used by pool and spa owners to sanitize their water fixtures. They are favoured for their low prices and ability to remain active in very strong sunlight.

Also known as cyanuric acid, a stabilizer is a compound that prevents sunlight from lowering the power of chlorine residuals.


This is the practice of adding enough chlorine to your pool or spa to reach 10ppm free chlorine residual.

Test Kit

Test kits are devices used by pool and spa owners in the Lower Mainland to monitor specific chemical residuals, levels or constituents or demands in the pool water. Kits usually contain reagents, vials, titrants, colour comparators and other materials necessary to perform tests. Test kits are used to determine pH levels, total alkalinity, free available chlorine, water hardness and levels of cynauric acid, iron and copper.

Test Strips
These are small plastic strips with pads attached. These pads contain reagents that can be used to test pool water for residuals, levels, constituents or demands. By dipping the strips into pool or spa water, users monitor the colour that emerges on the pads and compares that result to a standard set of colours to determine concentration.

Total Alkalinity (TA)
This refers to the total amount of the alkaline components in the water. TA acts as a buffer against rapid pH changes. The ideal range for this category is 125-150 ppm.


Turbidity refers to the cloudy pool water that occurs when particulates are too small to be filtered effectively. This results in murky water. Adding a clarifier, such as an organic polymer, will coagulate the particles and make the filter more efficient.

Undesirable Compounds

An undesirable compound is any substance introduced into pool or spa water either by swimmers or the environment itself that interfere with your pool’s water composition and conditions.


A vacuum is any device that uses suction power to collect dirt and debris from the bottom and sides of your pool.

Vinyl Liner
This is the vinyl membrane that acts as a container to hold water.

Water Clarifier

Also referred to as coagulant or fluctuant, a water clarifier is a chemical compound that pool and spa owners use to collect suspended particles so they may be removed either by vacuums or filtration pumps. There are two types of water clarifiers: inorganic salts of aluminum and other metals or water-soluble organic polyelectrolytes.

Also known as a skimmer weir, this is part of a skimmer that adjusts automatically to small changes in water level to assure a continuous flow of water to the skimmer. Weir also stop debris from re-entering the pool after the pump shuts off.

We service the following areas

Bowen Island

Lions Bay
Maple Ridge

New Westminster
North Delta
North Vancouver
Pitt Meadows
Port Coquitlam
Port Moody

West Vancouver
White Rock

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