Glossary - Swimming Pool Terms
ACID: Liquid (muriatic acid) or dry granular (sodium bisulphate) substance used to lower the pool's pH (toward a more acidic condition) or to lower total alkalinity levels.
ACID DEMAND: A titration test used to determine proper amounts of acid (or pH decreaser) to reach correct levels.
AIR BLEEDER ASSEMBLY: Located on the top of the filter and sometimes accompanied by a pressure gauge, the bleeder is opened to release air trapped in the filter.
ALGAE: 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.
ALGAECIDE: Meaning, to kill algae. Algaecides perform best as a backup to a routine sanitation program. They also help to kill airborne spores as they blow into the pool. A variety of algae treatment products are available including copper and silver compounds, poly-quat compounds, chlorine enhancers , and herbicides.
ALKALINE: Alkalis are best known for being bases (compounds with pH greater than 7) that dissolve in water.
ALKALINITY: Alkaline refers to the condition where the water's pH is above 7.0 (neutral) on the pH scale. It is the opposite of acidic. Alkalinity is the amount of carbonates and bicarbonates in the water, measured in "parts per million" (ppm) of Total Alkalinity.
ALUMINUM SULFATE: Also known as "alum;" this product 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.
AUTOMATIC POOL CLEANER: A device which agitates or vacuums debris from the walls and floor of the pool.
BACKWASH: The process of thoroughly cleaning the filter medium and/or elements by reversing the flow of water through the filter to waste.
BACTERIA: From a health perspective, the most dangerous micro-organisms which may be living in the pool water. Some are pathogens, which can cause infectious diseases.
BACTERICIDE: Kills bacteria. Chlorine is a bactericide and germicide. Silver algaecides are actually more bactericide, and are useful on pink "algae."
BALANCED WATER: 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.
BASE: Those chemicals of alkaline nature which will counteract the pH of an acid eventually neutralizing at 7.0. Common bases used around the pool would include Soda Ash, Sodium Bicarbonate, Sodium Carbonate, and Sodium Sesquicarbonate.
BASE DEMAND: A titration test used to determine proper amounts of base (pH increaser) to reach correct levels. For example, to raise pH from 7.2 - 7.6, your water may need 2 cups of soda ash.
BIGUANIDES: The name for a certain class of sanitizers using the polymer PHMB, the only non-halogen sanitizer available for pool and spa use. "Soft Swim" and "Baquacil" are manufacturers of this technology.
BICARBONATE: An intermediate form in the deprotonation of carbonic acid.
BLOWER: Plumbed into the spa return line, air is injected to produce fun bubbles and a hydrotherapy effect in the spa.
BOOSTER PUMP: Secondary to the filter pump, a booster pump is used to power an automatic pool cleaner such as Polaris or Letro.
BREAKPOINT CHLORINATION: 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.
BROMAMINES: A combined bromine - ammonia molecule. Unlike chloramines, which are strong smelling and offer no sanitizing properties, bromamine compounds continue to sanitize.
BROMINE: A member of the halogen family, commonly used as a sanitizer in spas, because of its resistance to hot water with rapid pH fluctuations.
BTU: British Thermal Unit. A unit of measurement for the use of gas by a gas appliance. Pool heaters are rated by their consumption.
BUFFER: A base such as Sodium Bicarbonate (Baking Soda), added to your pool will increase alkalinity which increases the buffering capacity of the pool; your pool's resistance to pH change.
BUFFERING CAPACITY: The ability of the pool to resist changes in pH, which prevents water balance. The buffering capacity is given by the alkalinity, a close cousin to pH. If your pH bounces, or resumes previous levels soon after adjustment your buffering capacity is too low. Check your total alkalinity.
CALCUIM: Calcium is a soft grey alkaline earth metal.
CALCIUM CARBONATE: Known as scale, crystalline deposits of calcium may form on your pool surfaces, equipment, or even line the insides of your pipes. Properly balanced water can prevent this.
CALCIUM CHLORIDE: The flaked calcium salt used to raise levels of Calcium Hardness in your pool water
CALCIUM HARDNESS: A titration test is used to determine levels of the mineral calcium dissolved in the pool water.
CAPACITY/VOLUME: The total number of gallons of pool water your pool contains (gallonage).
CAPACITOR: 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.
CARBON DIOXIDE: A gas, which when present in the water, provides necessary food for the growth of algae.
CARBONATE: Primary in the make up of total alkalinity and TDS.
CARTRIDGE: One type of filtration, the cartridge is a pleated, porous element through which water is passed through.
CAVITATION: A general term used to describe the behaviour of voids or bubbles in a liquid. Cavitation is usually divided into two classes of behaviour: 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.
CHANNELED SAND: When water has worked open "holes" in the sand and is streaming right through (without really going through the sand).
CHELATOR: A chelating agent is a water soluble molecule that can bond tightly with metal ions, keeping them from coming out of suspension and depositing their stains and scale onto pool surfaces and equipment. Similar to sequestering agents.
CHLORAMINES: The Chlorine molecule is strongly attracted to nitrogen and ammonia. When these two combine they form a chloramine, which are undesirable, foul smelling, space taking, compounds that require shocking the pool water to remove.
CHLORINE: A member of the halogen family of sanitizers, it's use in swimming pools is in the elemental form of a gas, liquid, granular, or tablet compound. When added to water it acts as an oxidizer, sanitizer, disinfectant, and all around biocidal agent.
TOTAL CHLORINE: The sum of combined and free chlorine levels. With a DPD test kit, one determines free available level, then total available. The difference, if any, is the level of combined chlorine.
CHLORINE GENERATOR: A miniature chlorine factory. This device creates its own sanitizer for your pool.
CHLORINATOR: Devices which allow for the safe controlled introduction of chlorine into the water.
CHLORINE DEMAND: 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.
CIRCUIT BREAKER: A switch which allows manual override of an electrical circuit. It also automatically breaks the circuit when current fluctuations are detected.
CIRCULATION SYSTEM: The circuit of plumbing which continuously carries the water out of the pool, through the pump and filter then returns it to the pool.
CLARIFIER: A clarifier is a chemical used as a coagulant of suspended micro particles. It helps the filter by clumping smaller particles into filterable sizes.
COAGULANT: The properties of a chemical used in the assemblage and precipitation of suspended material which may make the pool appear cloudy.
COMBINED CHLORINE: That portion of total available chlorine left over when free available is subtracted. The measure of chlorine which has already attached itself to other molecules or organisms. Most of this is made up of chloramines.
CONDUIT: A pipe, usually gray PVC or flexible PVC designed to carry wires from a source (i.e. time clock) to a load (i.e. pump motor).
CONTAMINANTS: Any micro-particle or organism which reduces water clarity or quality and may present a health hazard. All of our filtering, circulating, and sanitizing is directed here.
COPING: The capstone on top of the wall which finishes the edge around a pool or spa. It may be pre-cast Portland Stone or Sandstone.
COPPER: An effective algaecide. Copper as elemental is used in many pools in products.
COPPER SULPHATE: Similar to aluminium sulphate, this chemical provides a coagulating and flocculent function in water. Used mainly in ponds, a large amount of copper sulphate would stain a swimming pool.
CORROSION: The effects of a acidic pool environment. One in which the pH and/or alkalinity are very low. Corrosion in the form of etching, pitting, or erosion of pool equipment and surfaces is the result.
CYANURIC ACID: 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.
DEEP LEAF NET: Attached to a telescopic pole, a deep leaf net is a very useful tool in keeping the pool clean. Also, available in a ‘flat’ form.
DIATOMACEOUS EARTH: The filtering medium of the DE filter, this dry powder is the fossilized remains of the ancient plankton; diatom.
DIATOMACEOUS EARTH FILTER: A filter tank containing fabric covered grids which hold the DE powder up against the flow of the water.
DISINFECTANT: Chemicals or processes which work to destroy vegetative forms of microorganisms and other contaminants. Examples are chlorine, bromine and ionizers; also included are copper and silver algaecides.
DPD: A method of testing for chlorine levels in the pool water. DPD testing allows determination of total and free available chlorine levels which through subtraction gives us combined levels.
DRAIN: Also called the "main drain," this plumbing fitting is the start of one suction line to the pump and is usually situated at or near the centre bottom of the pool.
DRY ACID: Sodium bisulphate, a granular form of acid used to lower pH and alkalinity in the water. It is safer and less caustic than muriatic acid. Usually available as a "pH decreaser."
EFFLUENT: The water that flows out of the pump on its way through the filter, heating, treating equipment, and then returning to the pool. Also known as the pressure side.
ELECTROLYSIS: A method of separating chemically bonded elements and compounds by passing an electric current through them.
ENZYMES: Used in swimming pool formulations designed to break down and digest oils in a pool or spa similar to the way enzymes are used in oil spill clean-up efforts.
FILL WATER: Used in filling or adding to the water level. Whether from the hose or from a well, your fill water brings its own chemical make up and water balance (or lack thereof).
FILTER: A device used to remove particles suspended in the water by pumping water through a porous substance or material.
FILTER ELEMENT: A device inside a filter tank designed to entrap solids and direct water through a manifold system to exit the filter. Cartridge filter elements and DE filter grids are two examples.
FILTER MEDIUM: A finely graded material such as sand, diatomaceous earth or Zeolite that removes suspended particles from water passing through it.
FILTER PUMP: The device that pulls water from the pool and pushes it through the filter on its way back to the pool.
FILTRATION RATE: The rate of water pumped through a filter, in m3 per hour.
FLOCCULENT: Essentially the same as a coagulant, this chemical (such as alum) is used to combined suspended alkaline material and/or algae into a heavy gel, which sinks to the bottom for vacuuming to waste.
FLOW RATE: The quantity of water flowing past a specific point in a specified time, in m3 per hour.
FOAMING: A term used to describe surface foam on your water, esp. in spas/hot tubs. Foaming is caused by high TDS levels working in combination with soft water and oils. Certain low grade algaecides can foam when added to pool or spa. Use enzymes for foam control.
FREE CHLORINE: Free Available Chlorine is that which is active, not combined with an ammonia or a nitrogen molecule, and ready to react to destroy organic material.
GATE VALVE: The type that spins "lefty-loosey; righty-tighty."
GAS VALVE: An electronic valve in the pool heater that directs gas flow from the meter to the pilot and the burner tray.
GASKET: 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.
GUNITE: A dry mixture of cement and sand mixed with water at the "gun"; hence the name. A gunite operator "shoots" the pool's rough shape, while finishers trowel after.
HALOGEN: A member of the family of elements fluorine, bromine, chlorine and iodine.
HARD WATER: That water which is high in calcium hardness and other salts which, as such, resists soap being lathered.
HEATER: A device used to heat the water. It may be electric, fuel operated or solar powered heat.
HEAT EXCHANGER: A set of 8 or 10 ribbed copper tubes that absorb the heat produced below it and transfer it to the water cycling through its tubes.
HEAT PUMP: The opposite of an air conditioner, the heat pump's cooling coil removes heat from the air while the condenser coil transfers it to the water cycling through it.
HOT TUB: Usually considered a circular, wooden vessel filled with heated and circulated water.
HP: Horsepower (hp) is the name of several non-metric units of power. The most occurring conversion of horsepower to watt goes 1 horsepower = 745.7 watts.
HYPOCHLORITE: A family of chlorine compounds such as Calcium Hypochlorite and Lithium Hypochlorite, both granular, and the liquid Sodium Hypochlorite. When these compounds contact water, they release Hypochlorous Acid, the active sanitizing agent.
HYDROSTATIC PRESSURE: A force involving built up ground water which creates upward pressure beneath the pool shell.
HYDROSTATIC RELIEF VALVE: Fitting(s) installed in the floor of the pool designed to manually or automatically release hydrostatic pressure beneath the pool by allowing ground water into the pool.
IMPELLER: The rotating vanes of a centrifugal pump; its action creates the flow of water. The impeller is shaft driven by an electric motor.
IONIZER: An ioniser is a device mounted on your return line, and through which water flowing will receive charged metal ions. Manufacturers may use a copper anode and/or silver. Copper is an algaecide, while silver is known for its properties as a bactericide.
IRON: Usually introduced into the water from iron plumbing or from well water, Ferric Iron can stain surfaces, while Ferrous Iron will turn your water a clear green colour.
JET PUMP: Used in spas to provide additional thrust into the hydrotherapy jets.
LANGELIER INDEX: 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."
LATERALS: Elongated, capped plastic nipples at the bottom of a sand filter which are slotted to allow for water passage while keeping the sand in the filter tank.
MINERALS: Such as Calcium, Manganese, Magnesium, Nickel, Copper, Silver, Iron, Cobalt or Aluminium. Their presence in high non-chelated concentrations can lead to stains & scale when conditions are right.
MICROORGANISM: A living, breathing creature in your pool. The purpose of disinfectants are to remove such "infectants."
MECHANICAL SEAL: A seal behind the impeller which prevents water from running out along the shaft of a motor. aka; pump seal.
MOTOR: A machine for converting electrical energy into mechanical energy. Your motor is known as the dry end of the filter pump. It drives the impeller, which moves the water.
MPV: A Multiport valve. (See Below)
MSDS: Material Safety Data Sheet is a form containing data regarding the properties of a particular substance. An important component of workplace safety, it is intended to provide workers and emergency personnel with procedures for handling or working with that substance in a safe manner, and includes information such as physical data (melting point, boiling point, flash point, etc.), toxicity, health effects, first aid, reactivity, storage, disposal, protective equipment, and spill handling procedures. The exact format of an MSDS can vary from source to source.
MULTIPORT VALVE: A 4 or 6 position valve combining the functionality of several valves into one unit, revolutionizing pool plumbing. The six common functions are described below:
1.
FILTER: Keep it here 99%, except when backwashing, rinsing or wasting
RINSE: Use this setting for 20 seconds after backwashing to rinse tank
RECIRCULATE: Use this if the filter's broken; at least you're circulating.
BACKWASH: Use this setting to reverse the flow in the filter and send water out of the waste line. Make sure valves are open or hoses rolled out
CLOSED: Put here to close off flow from the pool, usually to work on the equipment. Do not operate pump with valve in closed position
2.
WASTE/DRAIN: Another filter bypass setting, but this setting sends the water out of the waste pipe (hose), instead of returning it to the pool. This setting is used to lower pool water level or to vacuum to waste.
MURIATIC ACID: The liquid dilution of Hydrochloric Acid used to lower pH and alkalinity, and to remove mineral stains and scale. Extremely caustic and corrosive.
NASCENT OXYGEN: A single oxygen atom, not yet bonded to anything. Extremely powerful oxidizer when harnessed.
NITROGEN: When combined with chlorine, nitrogen creates chloramines, which do not belong in our pool. Nitrogen can be found in many swimmer wastes (perspiration, suntan oil, hair tonics, etc.) or be introduced by other means.
NON-CHLORINE SHOCK: A granular form of potassium peroxymonopersulphate, used to oxidize materials such as microorganisms, contaminants or chloramines.
O-RING: A loop of rubber with a round (o-shaped) cross-section used as a mechanical seal or gasket. They are designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.
OXIDATION: The "burning up" of organic waste and compounds in the pool water. It also refers to what you may see on your metal pool surfaces if your water is corrosive. Rust is a form of this kind of oxidation.
OZONE: The molecule containing three atoms of oxygen; known to be a very powerful sanitizer. Ozone producing equipment creates this molecule by UV radiation or corona discharge generators.
pH: The scale of relative acidity or alkalinity, expressed in logarithmic numbers from 0 - 14, with 7.0 being neutral. What's really being measured is the hydrogen ion concentration. Some would say pH stands for Power of Hydrogen.
POTASSIUM PEROXYMONOPERSULPHATE: See non-chlorine shock.
PPM: Parts per million. A method of assigning value to certain concentrations of chemicals in the water. For example, alkalinity should be kept at 80-120 parts per million, by weight and in relation to the water it's dissolved in.
PRECIPITATION: To precipitate is to come out of solution; become insoluble by result of chemical action. Material forced out of solution, purposefully or accidentally, will then settle, stain or scale, or remain suspended in the water.
PRESSURE TEST: A test for the rate of water flow; also a test for leaks in plumbing by placing a line in question under pressure and waiting for the pressure to drop.
PRESSURE GAUGE: A device indicating pressure in a filter system. Provides a determination of how the system is operating, and informs us when a service or backwash is required.
PRESSURE SIDE: The return side of the plumbing. The section from the pump impeller towards the pool.
PRESSURE SWITCH: A switch used in pool heaters which opens when the flow rate is insufficient for safe heater operation. This disrupts the circuit in the heater, preventing it from firing.
PUMP: A mechanical wet-end, powered by an electric motor, which causes hydraulic flow and pressure for the circulation of the pool water.
PUMP STRAINER BASKET: A device placed on the suction side of the pump, which contains a removable strainer basket designed to trap large debris in the water flow without causing restriction.
PVC: Polyvinyl chloride, which is used to make flexible and rigid PVC pipe used for pool plumbing.
REAGENT: The chemical indicators used in testing water balance. (All the little bottles or tablets in your test kit).
RESIDUAL: Usually refers to free available chlorine levels remaining in the pool after initial treatment or activity with contaminants.
RESTRICTED FLOW: The term used to describe a condition preventing full flow of water. Restriction can occur with full skimmer or strainer baskets, obstructions in the plumbing, dirty filter, undersized plumbing or equipment , or placing devices like, heaters, cleaners or fountains in the circulation system. Restriction on the suction side creates higher vacuum, (or suction) while on the pressure side creates higher pressure.
SAND FILTER: A filter tank, usually fibreglass, filled with sand and gravel. The pump diffuses water over the top of the sand bed, and forces it through the sand and into the laterals on the bottom.
SANITISER: A chemical agent used to remove unwanted contaminants.
SCALE: Usually whitish in colour, scale forms on pool surfaces and equipment when mineral salts are forced out of solution. A scaling condition is one in which calcium hardness, pH and/or alkalinity levels are out of balance.
SEQUESTERING AGENT: A sequestering agent ties-up minerals tightly in solution, preventing their precipitation, which colours the water and/or stains the pool. These are commonly called stain & scale chemicals.
SKIMMER: A surface skimmer is a plumbing fitting set at water level, containing a weir mechanism and a debris basket. The skimmer is part of the suction side circulation system.
SKIMMER BASKET: Beneath the lid, the basket strains debris, as the first line of defence in filtering the water.
SHOCK: As a noun it loosely describes the products used in shocking, such as hypochlorites, potassium peroxymonopersulphate or hydrogen peroxide. As a verb it describes the act of bringing the sanitizer level up so high that breakpoint chlorination is reached. When breakpoint is reached, a "shock" or perhaps a "lightning bolt" is a better analogy, is sent through the water, tearing apart molecules and slashing through cell walls.
SODA ASH: A base, used to counteract an acidic condition by raising pH.
SODIUM BICARBONATE (baking soda): Another base, however its properties will increase alkalinity more than pH. Used to raise Total Alkalinity levels.
SODIUM BISULFATE: An granular form of acid, used to counteract a scaling condition by lowering pH and/or alkalinity.
SODIUM HYPOCHLORITE: Liquid chlorine used in pools, identical yet stronger than Clorox bleach.
SODIUM TETRABORATE: New technology that renders algae incapable of processing carbon dioxide, which they need to live.
SODIUM DICHLOR: A granular form of chlorine that is stabilized with cyanuric acid. Used for shocking and super-chlorination.
SOFT WATER: Water that has low calcium and/or magnesium content. Soap lathers easily in soft water.
SOLAR COVER : Sometimes called a thermal blanket, this cover floats on the surface magnifying the sun's rays to warm the water and also prevents chemical/heat/water evaporation.
SOLAR SYSTEM: Black mats of miniature plastic tubes through which water is pumped, absorbing the heat as it passes through. These mats are roof mounted with up & down plumbing connecting it.
SPA: A filtered, hot water vessel with hydrotherapy jets and air induction. Can be portable or installed permanently. Jacuzzi is a brand name.
STABILIZER: See Cyanuric acid. Stabilizers can be added directly to your pool to extend your chlorine efficacy. Cyanuric acid is already added to certain "stabilized" products such as Trichlor tablets and Sodium Dichlor.
STRAINER BASKET: The second line of defence is a basket at the pump. The holes in this are smaller than those in a skimmer basket, and prevent the pump impeller from clogging up.
SUCTION SIDE: The plumbing prior to and carrying water to the pump. This side is under vacuum pressure.
SUPER-CHLORINATION: Applying 7 - 10 times the normal amounts of chlorine to the pool as an added "boost" for contaminant removal. Some refer to super-chlorinating as being less than shocking, in that breakpoint thresholds are not reached, or the terms may be used synonymously.
TDS: See Total Dissolved Solids.
TEST KIT: A method used to test the water balance and sanitizing level of your pool water.
TIME CLOCK: A mechanical device that controls the timed operation of your electrical equipment, primarily your filter and booster pumps.
TITRATION: A method of testing for total alkalinity, calcium hardness and acid/base demand by adding a titrant, drop by drop until a colour change is observed.
TOTAL ALKALINITY: The ability of the pool water to resist changes in pH. The "buffering" capacity of the water. Additions of Sodium Bicarbonate will increase the levels, expressed in ppm.
TOTAL DISSOLVED SOLIDS (TDS): A measure of everything that has ever dissolved in the water; all the matter that is in solution. High TDS levels can oversaturated your water, causing all sorts of reactions.
TURBIDITY: Cloudy, dull, hazy water, due to micro particle suspension.
TURNOVER: The amount of time it takes your pump to move all the water in your pool through the filter and back again. Usually, domestic pools are designed for a 5 to 6 hour turnover.
ULTRA VIOLET LIGHT: Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. It is so named because the spectrum starts with wavelengths slightly shorter than the wavelengths humans identify as the colour violet (purple).
ULTRA VIOLET LIGHT TREATMENT: Using UV wavelength radiation to destroy contaminants in water. UV light is also used to create ozone molecules for the same purpose.
UNDERDRAIN: The lower collection system in a filter which directs filtered water back towards the pool. It also distributes water in reverse during backwashing. See laterals.
VACUUM: Refers to the low pressure condition created in the suction line. Also refers to the cleaning process of sucking leaves, algae and debris from the pool floor.
VENTURI: Increasing water velocity by restricting pipe size usually accomplished by a spa jet.
VINYL LINER: One type of interior pool finish. The liner is draped over a sand or cementitious floor, and locked into the top of the pools wall.
WEIR: The device in a skimmer that controls the amount of water coming into the skimmer, and keeps debris inside.
WINTER DEBRIS COVER: These stretch tightly across the pool like a trampoline to create a barrier to sun and debris.