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B.E.P.: The best efficiency point. It is the point where the power coming out of the pump (water horsepower) is the closest to the power coming into the pump (brake horsepower) from the driver. This is also the point where there is no radial deflection of the shaft cause by unequal hydraulic forces acting on the impeller.

B.H.P.: Brake horsepower. The actual amount of horsepower being consumed by the pump as measured on a pony brake or dynamometer.

Back plate: Used in some centrifugal pumps to position the stuffing box and provide an impeller wear surface.

Back pull out pump: A design that allows the wet end of the pump to be left on the piping when the power end and adapter are removed. A.N.S.I. pumps are designed this way.

Back to back double seal: The rotating seal faces are facing in opposite directions. The worst possible configuration. In the past this term was used to describe a higher barrier fluid pressure between dual mechanical seals.

Back vanes: See end-suction pump.

Backfill: The repositioning of the soil after construction of a pool.

Backflow preventer: A device designed to keep water in the sprinkler system from flowing back into the service line. Backflow prevention is required in most areas.

Backflow: A reverse flow in water pipes. A difference in water pressures pulls water from sources other than the well into a home’s water system, for example waste water or flood water. Also called back siphonage.

Backflow Preventor (Backflow Prevention Device): A device used to prevent the backflow of water and avoid cross-contamination. In plumbing applications, backflow preventers used to avoid backflow of utility water (such as the one used for irrigation) into the domestic plumbing system, which may occur due to gravity flow or siphoning effect. In heating applications, backflow prevention devices used to avoid cross-contamination of domestic water with water from the heating system.

Backwash: The process of flow reversal to clean a filter and to restore it to the normal clean condition for filtering with a minimum resistance to flow through the media.

Backwash-1-: The process of thoroughly cleaning the filter medium and/or elements by reversing the flow of water through the filter to waste.

Backwash-2-: 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 “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.

Backwash Cycle: The operating time, after the filter cycle, required to completely clean the filter.

Backwash Piping: The pipe extended from the backwash outlet of the filters to a terminus at the point of disposal.

Backwash Rate: The rate of application of water through a filter during the cleaning cycle expressed in gallons per minute per square foot of effective area.

Bacteria: Any of a class of microscopic living organisms 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-generative), saprophytic (digests chemicals already in their environment) or parasitic. Some are helpful and some are harmful. “Good” bacteria aid in pollution control by consuming and breaking down organic matter and other pollutants in septic systems, sewage, oil spills, and soils. However, “bad” bacteria in soil, water, or air can cause human, animal, and plant health problems.

Bacteria-1-: 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."

Bactericide-1-: Material capable of inhibiting or destroying bacteria. Function is known as bactericidal.

Bacteriostatic: Material capable of reducing the rate of bacterial growth. Sometimes confused with bactericidal.

Baffle: A specially constructed component within the WA1000 mercury tilt switch designed to regulate the flow of mercury, resulting in a wide angle between on and off.

Balance Ratio: A 70/30-balance ratio means that 70% of the seal face closing area is seeing the stuffing box pressure and 30% is not seeing the pressure.

Balance 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.

Balanced seal: A design in which the seal face closing area is reduced to lower the closing force, and reduce the heat generation between the faces.

Ball bearing: Consists of an inner race, an outer race, and a series of balls between them. Often called a precision or anti friction bearing.

Ball or Globe Valve: These valves can be adjusted but are less susceptible to cavitation than a gate valve.

Ball Valve:  A quarter-turn valve where a closing mechanism consists of a sphere encased in a water–tight material (usually Teflon). Similar to other types of valves, ball valves are available in threaded, solder, compression, PEX and other connection types and range in sizes from 1/8” to 4”. Ball valve’s body may be manufactured from brass, bronze, steel and even plastics, such as PVC.

Ball Valve-1-: A device with a hollowed out ball inside which can be turned with an external handle to decrease or increase flow.

Bar: Metric term for one atmosphere of pressure.

Barbed Fitting: As opposed to a threaded fitting, rings projecting outward around fitting designed to grip hose. Usually measured in O.D. (outside diameter) , as opposed to hose measured in I.D. (inside diameter).

Barometric pressure: Tthe same as atmospheric pressure, the pressure in the local environment. Barometric pressure is a term used in meteorology and is often expressed in inches of Mercury.

Barrier fluid: The high-pressure fluid that is circulated between two mechanical seals. The fluid should enter the bottom and leave the top to prevent air pockets.

Barrier PEX: PEX tubing with oxygen barrier. Oxygen barrier is a layer of special polymer, usually applied to the external surface of the PEX tubing to reduce diffusion of air molecules through the pipe’s walls.

Barrier: Tubing with oxygen barrier. Oxygen barrier is a layer of special polymer, usually applied to the external surface of the tubing to reduce diffusion of air molecules through the pipe’s walls.

Base: a substance that has a pH of more than 7, which is neutral. A base has less free hydrogen ions (H+) than hydroxyl ions (OH-).

Base-1-: 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.

Base flow: sustained flow of a stream in the absence of direct runoff. It includes natural and human-induced stream flows. Natural base flow is sustained largely by ground-water discharges.

Base plate: The pump and motor mount on this unit. The pump and motor feet closest to the coupling should be doweled to the base plate.

Baseboard Tee: A brass/bronze tee fitting where one of the side outlets is used for air bleeding purposes.

Baseboard: An encased aluminum finned copper or cast iron finned tube type radiator used for heating applications. The major visual difference between traditional cast iron/aluminum radiators and baseboard radiators is their shape and size. Whereas regular radiators tend to be high (up to 3 ft) and short (up to 4-5 ft), baseboard radiators are usually low (up to 1ft) and long (up to 8ft).

Baseplate:  All pumps require some sort of steel base that holds the pump and motor and is anchored to a concrete base.

Basic Pump Components: The driver (most likely an electric motor) supplies the power necessary to rotate or spin an impeller; the volute case and seal plate, which direct the water to where you want it to go and builds the pressure to drive the water in the direction desired; the impeller moves the water and adds velocity.

Basket Strainer: A device which acts as a filter for a flow of liquid or slurry. Large particles are trapped in the strainer and not allowed to continue through the system.

Bather: Any person using a pool, spa or hot tub and adjoining deck area for the purpose of water sports, recreation or related activities.

Batteries: A device that converts chemical energy into electrical energy. Batteries produce direct current.

Battery Capacity: The electric output of a cell or battery on a service test delivered before the cell reaches a specified final electrical condition and may be expressed in ampere-hours, watt-hours, or similar units. The capacity in watt-hours is equal to the capacity in ampere-hours multiplied by the battery voltage.

Battery Charger: A device capable of supplying electrical energy to a battery.

Battery Voltage, final: The prescribed lower-limit voltage at which battery discharge is considered complete. The cutoff or final voltage is usually chosen so that the useful capacity of the battery is realized. The cutoff voltage varies with the type of battery, the rate of discharge, the temperature, and the kind of service in which the battery is used. The term "cutoff voltage" is applied more particularly to primary batteries, and "final voltage" to storage batteries. Synonym: Voltage, cutoff.

Battery: A device that transforms chemical energy into electric energy. The term is usually applied to a group of two or more electric cells connected together electrically. In common usage, the term "battery" is also applied to a single cell, such as a household battery. Battery Types -- There are, in general, two types of batteries: primary batteries, and secondary storage or accumulator batteries. Primary types, although sometimes consisting of the same active materials as secondary types, are constructed so that only one continuous or intermittent discharge can be obtained. Secondary types are constructed so that they may be recharged, following a partial or complete discharge, by the flow of direct current through them in a direction opposite to the current flow on discharge. By recharging after discharge, a higher state of oxidation is created at the positive plate or electrode and a lower state at the negative plate, returning the plates to approximately their original charged condition.

Battery-Charging Rate: The current expressed in amperes at which a storage battery is charged.

Bearing Housing: Same as end bell. Houses the bearing of motor and supports the rotor.

Bearing Life: Rating life, L10 (B10), is the life in hours or revolutions in which 90% of the bearings selected will obtain or exceed. Median life (average life), L50 (B50), is the life in hours or revolutions in which 50% of the bearings selected will obtain or exceed.

Bearing: Supports the rotating shaft and allows it to turn with a minimum amount of friction. Could be either sleeve or anti-friction type.

Bearings: Three types generally used in electric pump motors: ball; sleeve; Kingsbury.

Bearings-1-: Bearings reduce friction and wear while supporting rotating elements. When used in a motor, they must provide a relatively rigid support for the output shaft.Bearings act as the connection point between the rotating and stationary elements of a motor. There are various types such as roller, ball, sleeve (journal) and needle. Ball bearings are used in virtually all types and sizes of electric motors. They exhibit low friction loss, are suited for high- speed operation and are compatible with a wide range of temperatures. There are various types of ball bearings such as open, single shielded and sealed.

Bedrock: the solid rock beneath the soil and superficial rock. A general term for solid rock that lies beneath soil, loose sediments, or other unconsolidated material.

Beginners Area: Those water areas in pools, spas and hot tubs which are three feet (3) or less in water depth.

Bellows: Can be manufactured from metal or non-metallic materials to eliminate flexing, rolling or sliding elastomers in mechanical seal designs.

Belt- Or Chain-Drives: A mechanism for transferring mechanical power between two places and is a common means of motivating large agricultural pumps.

Bend Support: Installation accessory used both in radiant heating and PEX plumbing applications to provide a smooth 90-degree turn and support for PEX tubing. Various designs of bend supports include types with mounting ear or strap. Usually made from galvanized steel or fiber-reinforced plastic.

Bernoulli's Law: A moving stream of liquid or gas exerts less sideways pressure than if it were at rest. The result is that things seem to be drawn into the stream, but the higher pressure from outside is really pushing them in.

Best Available Technology: The water treatment(s) that EPA certifies to be the most effective for removing a contaminant.

Best Efficiency Point (B.E.P.): The point on a pump's performance curve that corresponds to the highest efficiency. At this point, the impeller is subjected to minimum radial force promoting a smooth operation with low vibration and noise.

BHP: Brake Horsepower - the measured quantity of energy that must be supplied by the driver for the pump to operate successfully at the given conditions.

Bicarbonate: An intermediate form in the deprotonation of carbonic acid.

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.

Bill Of Materials (BM): List of parts that are assembled into a pump at the factory.

Binders: When used in reference to cartridge filters, refers to chemicals used to hold, or bind, short fibers together in a filter. Also may refer to various chemicals used to bind polymeric compounds in products such as plastic bottles.

Bingham plastic: A fluid that behaves in a Newtonian fashion (i.e. constant viscosity) but requires a certain level of stress to set it in motion.

Biofilm: An aggregation of active, multi-layered microbes found on surfaces and in particular inside tubing and pipes. May be difficult to remove by chemical means due to multiple layers and lack of fluid dynamics at surfaces where it resides.

Bipolar Transistor: A type of transistor with three terminals that is made from a doped semiconductor material; a specific kind of transistor used to send currents in two different directions. Its primary purpose is for use in electrical devices to amplify or change electrical signals.

Black Water: Raw human sewage.

Black Water-1-: Wastewater from the toilet, which contains most of the nitrogen in the sewage.

Black Wire: Only hooked up to a circuit breaker and would tell a U. S. electrician that the wire may not be safe to touch as it may have live voltage on it.

Bleeder Orifices: A device used where submersible pumps are installed with an air over water tank to maintain air pressure in the tank to help prevent the tank from becoming water-logged.

Blinding: The fouling or plugging of pores in a membrane, usually by a gel-like substance.

Blower: Plumbed into the spa return line, air is injected to produce fun bubbles and a hydrotherapy effect in the spa.

BOD (Biochemical Oxygen Demand): Measure of the amount of oxygen required by bacteria for stabilizing material that can be decomposed under aerobic conditions. BOD is a commonly used determinant of the organic strength of a waste.

Body Feed: The continuous addition of small amounts of filter aid during the operation of a diatomaceous earth filter.

Boiler Drain Valve: Typically a multi-turn valve used to drain the water from boilers, water heaters, as well as entire plumbing and heating systems.

Boiler Feed Valve: Usually either a pressure reducing valve, or a combination of pressure reducing valve with backflow prevention device – used to fill the heating system and the boiler with fresh water when system pressure drops below pre-set value.

Boiler Reset Control: An electronic module designed to improve the efficiency of the hot water heating system by regulating supply water temperature based on outdoor temperature.

Boiler room: Also known as mechanical room, is a dedicated space for for heating system components and parts, including, but not limited to, the boiler itself.

Boiler: Equipment used to heat the water or steam for heating applications. Unlike water heater, which is used to heat fresh water, boiler is designed to re-heat water, which is circulated in a closed loop. Boilers can be conventional, modulating and condensing and can use various fuel types, including natural gas, oil, electricity, wood, pellets and others.

Bonding: The purpose of a electrical bonding system is to ensure that metals on a boat are at the same voltage potential.  This provides two major benefits:  electrical safety for the above water metals, and corrosion protection for the underwater metals.  When bonded, underwater metals cannot be damaged by stray electrical currents originating from within the boat (e.g., a defective bilge pump, float switch or wire splice).  When the bonding system is then connected to sacrificial anodes, all bonded underwater metals are protected against galvanic corrosion.

Bonding-1-: Connecting together all the metal items (ladders, diving platforms, pumps, etc.) around a pool or spa with a heavy wire (the “bonding wire”), so that there can be no difference in voltage between them. This helps prevent electrical shocks from pool equipment.

Booster Pump: A pump that adds pressure to existing pressure in a water system.

Booster Pump-1-: Secondary to the filter pump, a booster pump is used to power an automatic pool cleaner such as Polaris or Letro.

Booster Pump System: A system whereby one or more hydrojets are activated by the use of a pump which is completely independent of the filtration and heating system of a spa. In other uses it is generally a pump and pressure tank controlled by a pressure switch or other device.

Booster Station: A pumping system used to amplify water pressure.

Bourdon pressure gauge: The Bourdon tube is a sealed tube that deflects in response to applied pressure and is the most common type of pressure sensing mechanism.

Bow: Manufacturer of PEX tubing and PVC fittings.

Bowl (vertical turbine pump): The casing of one stage a multi-stage vertical turbine pump.

Bowl-Style Construction: Features multi-vane diffusers in bowls that thread or bolt together for ease of assembly and disassembly. Bowl-style submersible turbines use mixed flow impellers.

B-PEX: PEX tubing manufactured using silane method or cross-linking. This type of PEX is usually installed using Crimp, Clamp, Press or Push-Fit connection systems.

Brackets: In various plumbing, heating or venting applications, brackets usually provide fixed support for pipe, group of pipes or system components.

Brackish water: Water containing between 1000 and 15000 mg/l of dissolved solids is generally considered to be brackish.

Brake Horsepower (BHP): The measured quantity of energy that must be supplied by the driver for the pump to operate successfully at the given conditions.

Brake Horsepower-1-:  Pump performance can be expressed in horsepower using the following formula: Brake HP = GPM x Ft./Head / 3940.

Brakes: An external device or accessory that brings a running motor to a standstill and/or holds a load. Can be added to a motor or incorporated as part of it.

Brass: Alloy of copper and zinc. Widely used in manufacture of fittings, valves and other components for plumbing and heating applications.

Brass-1-:  Generally good corrosion resistance. Susceptible to de-zincification in specific applications; excellent machinability. Primary uses for wrot brass are for ball valve stems and balls, and iron valve stems. A forging grade of brass is used in ball valve bodies and end pieces.

Brazetek: Manufacturer of brazed plate heat exchangers.

Breakaway Torque: Same as Starting Torque or Lock Rotir Torque -- The torque developed by the motor when starting or when stalled (rotor blocked).

Breakdown Torque (BDT): Same as Pull Out Torque or Maximum Run Torque. Usually is the maximum value of torque that a motor will develop without a sudden decrease in speed(breakdown).

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.

Breakthrough: The first appearance in the effluent of an adsorbate of interest under specified conditions.

Breather or Breather Drain: Plug type device to provide drainage of condensation or water from motor.

Bridge Or Bridge Rectifier: A set of solid state diodes that convert AC power to DC power.

Bridging (OR Salt Bridging): The caking of salts in a dry water softener tank which causes failure of the liquid or brine beneath the dry salt to become saturated. The net result of bridging is insufficient salt to properly regenerate the resin.

Brine (Same as Reject Water): One of two streams of fluids generated by a Distiller or Reverse Osmosis unit. It contains the impurities removed from the feed water. Characteristically, 30,000 to 300,000 ppm.

Brinnell hardness: A method of measuring the hardness of metal parts and hard seal faces. Above 350 the standard machining operations of turning, boring, drilling, and tapping become uneconomical.

Bromamines: 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.

Bromide: A compound of bromine. Two of the salts, Sodium and Potassium Bromide, are sometimes used to produce a disinfectant or algaecide.

Bromine: An element which is sometimes used in pool water purification. A dark, heavy, reddish-brown liquid in its normal state. Closely related to chlorine.

Bronze: One of the first alloys developed in the bronze age is generally accepted as the industry standard for pressure-rated bronze valves and fittings. Bronze has a higher strength than pure copper, is easily cast, has improved machinability, and is very easily joined by soldering or brazing. Bronze is very resistant to pitting corrosion, with general resistance to most chemicals less than that of pure copper.

Bronze-1-: An alloy of copper and tin.

Brush: A piece of current conducting material (usually carbon or graphite) which rides directly on the commutator of a commutated motor and conducts current from the power supply to the armature windings.

BTU (British Thermal Unit): A unit of measurement for the use of gas by a gas appliance. Pool heaters are rated by their consumption.

BTU-1-: Abbreviation for British Thermal Unit, a traditional energy measurement unit. Represents the amount of energy (heat) needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

Buffer fluid: The low pressure fluid that is circulated between dual mechanical seals.

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.

Buna N: Buna N is a synthetic rubber also known as Nitrile or NBR. It is presently the seal industry's most widely used and economical elastomer, Buna N  combines excellent resistance to petroleum-based oils and fuels, silicone greases, hydraulic fluids, water and alcohols, with a good balance of such desirable working properties as low compression set, high tensile strength, and high abrasion resistance.

Buna N-1-: Some times called Nitrile. A common elastomer used in the sealing of oil or water. Sensitive to Ozone attack and therefore has a short shelf life.

Bushing: A close fitting support device used to restrict flow between two liquids, thermally isolate a hot liquid, support the rotating shaft, break down pressure etc. Commonly made of carbon or Teflon.

Butterfly Valve: From a family of valves called quarter turn valves, the butterfly is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks the liquid flow. When the valve is open, the disc is rotated a quarter turn so that it allows unrestricted liquid passage.

Bypass line: a line used to connect the discharge side of the pump to a low pressure area, often the pump's suction tank, for the purpose of moderating the flow in the system and/or to bring the pump's operating point within a favorable area of the pump's performance curve.

Bypass line-1-: Used to either re-circulate fluid from the pump discharge to the stuffing box, the stuffing box to the pump suction, or the pump discharge to a lower pressure point in the system.

Bypass Valve: Used in heating applications, this valve allows to bypass excess water pressure, thus reducing stress on the system and it’s components.

Bypass Valve-1-: Valve  that allow fluid to be recirculated if a given pressure limit is exceeded.