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E.P.R.: Ethylene propylene rubber. The most common elastomer used in the sealing of water based and higher pH materials. Cannot be used in petroleum products.

Eccentric Reducer - Also called a Bell reducer, is a pipe fitting designed with the smaller outlet off center to the larger end, allowing it to align with only one side of the inlet. The eccentric reducer must be installed with the straight side up to prevent trapping air at the pump suction. Eccentric reducers eliminate noise and isolate vibration in the pipeline, reduces stress, eliminates electrolysis and protects against start-up surges.

Eccentric- The shape of a pipe or fitting meaning off-center, not exactly circular in shape.

Eff. % or Pump Efficiency (percent) - the difference between the LHP (Liquid Horsepower) and BHP (Brake Horsepower). LHP is the amount of HP required to get a certain flow and head out of the pump. BHP is the cost to make that happen. Pump efficiency is always going to be less than one because you can never get more out then you put in. It is a ratio of flow and head out vs. electricity in. Efficiency % is about what goes in vs. what you get out OR what I use verses what I loose OR the wattage we use or pay for vs. the wattage used to accomplish our task.

Effective Filter Area - Permanent Medium Type: The effective filter area is the filter surface that is perpendicular to the flow direction. Cartridge Filter: The total effective filter area shall be the cartridge area that is exposed to the direct flow of water. This excludes cartridge ends, seals, supports and other areas where flow is impaired.

Efficacy: The power to produce an effect. Chlorine's efficacy is affected by many factors, including the sun, water balance, and the water's chlorine demand.

Efficiency: A ratio of total energy output to the total energy input expressed as a percent.

Efficiency-1-: Power out of the equipment divided by power in.

Efficiency-2-:  Power out of the equipment divided by power in.

Efficiency-3-: The efficiency of a pump can be determined by measuring the torque at the pump shaft with a torque meter and then calculating the efficiency based on the speed of the pump, the pressure or total head and flow produced by the pump. The standard equation for torque and speed provides power. The power consumed by the pump is proportional to total head, flow, specific gravity and efficiency. Flow and total head are measured and then the efficiency can be determined. The efficiency is calculated for various flow rates and plotted on the same curve as the pump performance or characteristic curve. When several performance curves are plotted, the equal efficiency values are linked to provide lines of equal efficiency. This is a useful visual aide as it points out areas of the various pump curves that are at high efficiency, which will be the preferred areas or areas that the selected pump should operate within. The highest efficiency on a given pump curve is known as the B.E.P. (best efficiency point).

Efficiency (Motor): A motor's efficiency is a measurement of useful work produced by the motor versus the energy that it consumes (heat and friction). An 84% efficient motor with a total watt draw of 400W produces 336 watts of useful energy (400 x .84 = .336W). The 64 watts lost (400 - 336 = 64W) becomes heat. Electric motors, and everything else involved with power production or conversion, have an efficiency. The efficiency of a motor is the ratio of useful mechanical power at the pulley to the electrical power input. A perfect motor would have an efficiency of 1.0 or 100%, meaning that all the electrical power input would appear as mechanical power. All electrical power that does not contribute to mechanical power is loss. The loss is from several sources, including heat and friction. Full-load motor efficiencies usually range from 50% to 95%. Fractional horsepower motors usually have efficiencies under 75%. Standard 1-10 HP motors have efficiencies between approximately 75% and 85%. Note that efficiency decreases as the load decreases from maximum, and drops severely for less than 50% of full load. Note that the rated horsepower takes this into account; you do not derate the nameplate rating by the efficiency. What the efficiency tells you is how much electrical power you are wasting. Spending more money on a higher efficiency motor will reduce your electric bill. For example, a 1 HP 75% efficient motor would require 746W/0.75 or 995W of electrical power. An 85% efficient motor would require 878W. This would save about 1.5 cents per hour of operation at Philadelphia area residential electric rates. If the motor runs continuously, the savings would be about $131 per year.


Effluent: Sewage or waste water which has undergone some pretreatment. Effluent water may contain small solids and/or stringy material (lint, hair, etc.). Effluent is generally defined as 3/4” solids or less.

Effluent-1-: 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.

Effluent-2-: Water that flows from a sewage treatment plant after it has been treated.

Ejector Package: When supplied for use with a jet pump, its components include a housing, a venturi, and sealing components. When water is pushed through the venturi, a low pressure region is created that siphons external water into the water flow, which is then delivered to the system water supply.

Ejector Vane: Located on the back side of the impeller, the ejector vane creates positive pressure that prevents debris from collecting around the shaft seal.

Ejector: A device consisting of a body, nozzle, and venturi tube that increases the pressure output of a jet pump. The nozzle increases the velocity of the water, then the venturi tube converts the velocity to pressure.

Elastic range: The stressed part retains its memory and returns to its original shape.

Elastomer: A rubber like material that, when compressed and then released will return to 90% of its original shape in less than five seconds.

Elbow: A 90 or 45 degree plumbing fitting. Used where your pipes take a turn.

Electric Motor (Squirrel Cage Induction Type):  A motor whose name is derived from the similarity between the motor windings (which may use conductive bars connected together at both ends by shorting rings forming a cage-like shape) and a squirrel cage/hamster wheel. These are the most common type of industrial AC electric motors, being rugged and requiring neither a separate DC power source nor ship-rings. They are constant speed devices when energized by a constant frequency AC supply.

Electrical Charge: Movement of electrons into another orbit.

Electrical Energy: A wave that moves along columns of electrons around a conductor. The energy itself is contained in the electromagnetic fields connected to those electrons and moves very fast (almost the speed of light), used up when it reaches a load.

Electrical Relay: A switch operated by electricity. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off so relays have two switch positions and most have double throw switch contacts. Can be controlled using low power and can control multiple loads.

Electrical Unbalance: In a three-phase supply, where the voltages of the three different phases are not exactly the same. Measured as a percent of unbalance.

Electricity: Energy in the form of a flow of electrons.

Electricity-1-: Indefinable as it is used to mean different things.

Electrochemical Couple: The system of active materials within a cell that provides electrical energy storage through an electrochemical reaction.

Electrode: An electrical conductor through which an electric current enters or leaves a conducting medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum. For electrolytic solutions, many solids, and molten masses, an electrode is an electrical conductor at the surface of which a change occurs from conduction by electrons to conduction by ions. For gases and vacuum, the electrodes merely serve to conduct electricity to and from the medium.

Electrolysis: A method of separating chemically bonded elements and compounds by passing an electric current through them.

Electrolysis: A process involving chemical change caused by the passage of an electric current through a liquid.

Electrolysis-1-: Decomposition of metal due to flow of electrical current.  Electrolysis is similar to corrosion, in the fact that it is the process of deteriorating metal by a reaction process. Although the results are the same, corrosion and electrolysis differ by the time required for the process and what usually causes the process. Electrolysis is a reaction between metal and electrical energy. Electrolysis occurs when electrical current is "leaking" into the water and can come from a variety of things such as improperly grounded electrical devices and power circuits, old electrical devices in contact with the water, batteries in boats, etc. Also, since this process includes a stronger reaction agent (electricity), the process is much quicker than corrosion.  See Sacrificial Zinc Anode .

Electrolyte: A chemical compound which, when fused or dissolved in certain solvents, usually water, will conduct an electric current. All electrolytes in the fused state or in solution give rise to ions which conduct the electric current.

Electrolytes:  Substances that conduct electric current are called electrolytes.  They are formed as a result of a separation into positively and negatively charged particles called ions, which migrate toward and ordinarily are discharged at the negative and positive terminals of an electric circuit, respectively. The most familiar electrolytes are acids, bases, and salts, which ionize when dissolved in such solvents as water. Many salts, such as sodium chloride, behave as electrolytes when dissolved in water.  Pure water will not behave as an electrolyte. Seawater is an excellent electrolyte. The presence of a large amount of dissolved salts, sodium chloride (NaCl), that are ionized make it an excellent conductor. The chloride ions is particularly aggressive as it causes a breakdown of passivity causing pitting, crevice corrosion and stress corrosion cracking on most stainless steel grades.

Electromagnetic Force: The movement of electrical energy along a path around a conductor (wire).

Electron: The smallest part of the atom that revolves around the positively charged nucleus. Electrons have a negative charge, and they are the basic source of electricity.

Electronic Relay: Senses the pump motor amp draw and the normally closed switch opens, disconnecting the wire going from the relay to the capacitor taking the start windings out of the circuit.

Electrons: A stable negatively charged elementary particle with a small mass that is a fundamental constituent of matter and orbits the nucleus of an atom.

Electropositivity: The degree to which an element in a galvanic cell will function as the positive element of the cell. An element with a large electropositivity will oxidize faster than an element with a smaller electropositivity.

Elevation: The distance between the ground level at the pump and the ground level at the well. There is no elevation when the pump is installed right at the well.

Elevation-1-: The vertical distance between the level where fluid enters a pipe and the level where it leaves; is measured from the datum plane to the highest point. It is associated with the discharge side of a pump and must be added to the Total Discharge Head if the inlet is lower than the outlet and subtracted if the inlet is higher. As a rule of good installation practice, however, pipes should slope continuously upward from the inlet to the outlet to prevent entrapment of air.

Empty Bed Contact Time: A measurement of the duration of contact between water and the media through which it is flowing, typically used in reference to carbon beds.

Enclosure (ENCL): Enclosure refers to the housing in which the controller is mounted. Enclosures are available in designs for various environmental conditions.

End Bell: Same as bearing housing. Houses the bearing of motor and supports the rotor.

End suction pump: A typical centrifugal pump, the workhorse of industry. Also known as volute pump, standard pump, horizontal suction pump. The back pull out design is a standard feature and allows easy removal of the impeller and shaft with the complete drive and bearing assembly while keeping the piping and motor in place.

End-of-Discharge Voltage: The voltage of the battery at termination of a discharge.

Endotoxin: Bacterial lipopolysaccharide, a substance released from the cell walls of gram-negative bacteria when the organism is broken down.

Endurance limit: Beyond this point the metal will fatigue without increasing the stress.

Energy Density: Ratio of cell energy to weight or volume (watt-hours per pound, or watt-hours per cubic inch).

Energy gradient: See Hydraulic gradient.

Energy loss: The wasted energy due to internal resistance.

Energy: Cannot be created or destroyed, only converted.

Energy-1-: Output capability; expressed as capacity times voltage, or watt-hours.

Engine Driven Pump: A type of pump which uses an electric or hydraulic motor as its driver or motive force.

Enhanced-Flow STEP System: A private sewage system that requires a pump. An Effluent Pump lifts a predetermined volume of collected septic overflow to a distribution box or manifold for gravity flow to an absorption field. Enhanced-Flow Systems have the advantage of flexibility in locating the absorption field as well as improved performance compared to strictly gravity flow systems. By pumping a predetermined volume each cycle, the absorption field has time to stabilize between cycles. Loss of effectiveness in hard soils and high water tables and progressive plugging of drain holes and absorption areas are disadvantages.

Enthalpy: A thermodynamic property of a fluid. The enthalpy of a fluid consist of the energy associated with the fluid at a microscopic level (related to the temperature of the fluid) plus the energy present in the form of pressure at the inlet and outlet of a system.

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.

EOC Voltage: The terminal voltage of a secondary cell or battery at the end of charging.

EOD Voltage-1-: The terminal voltage of a cell or battery which is specified as representing the end of discharge.

EPDM: EPDM is a terpolymer elastomer made from ethylenepropylene diene monomer. EPDM has good abrasion and tear resistance and offers excellent chemical resistance to a variety of acids and alkalines.  It is susceptible to attack by oils and is not recommended for applications involving petroleum oils, strong acids, or strong alkalines. It has exceptionally good weather aging and ozone resistance. It is fairly good with ketones and alcohols and has an excellent temperature range from -20°F to 250°F.

EPDM-1-: Is an elastomer made from ethylenepropylene diene monomer. EPDM has good abrasion and tear resistance and offers excellent chemical resistance to a variety of acids and alkalines. It is susceptible to attack by oils and is not recommended for applications involving petroleum oils, strong acids, or strong alkalines. It has exceptionally good weather aging and ozone resistance. It is fairly good with ketones and alcohols and has an excellent temperature range from -20°F to 250°F.

EPDM-2-:is a type of synthetic rubber. The E refers to ethylene, P propylene, D to diene and M refers to its classification in ASTM standard D-1418. The M class includes rubbers having a saturated chain of the polyethylene type. EPDM is resistance to a wide range of chemicals for general purpose use.

Epoxy Encapsulated (Potted) Pumps: These pumps feature an epoxy-encapsulated motor, plastic housing, and radial lip seal on the motor shaft. They provide enough power to effectively operate a water garden, statuary or tabletop fountain. Algae build-up does not effect these small, powerful workhorses. In fact, they may even be used in some harsh, industrial-type applications. These "potted" pumps are usually more compact in size than an oil-filled pump of equal flow capacity.

Epoxy Encapsulated (Potted): Pumps featuring a epoxy -encapsulated motor, plastic housing, and radial lip seal on the motor shaft.

Equilibrium: The condition where the forces applied to an object are in balance.

Equipment head difference: the difference in head between the outlet and inlet of an equipment.

Equipment: Refers to any device in the system other than pipes, pipe fittings and isolation valves.

Equivalent Length Of Pipe: Pipe fittings and valves were tested and values assigned for the head loss measured through them. Instead of assigning a factor, as in the "K" factor method, an "equivalent length of pipe in linear feet" value was assigned.

Equivalent length: A method used to establish the friction loss of fittings (See next figure). The equivalent length of the fitting can be found using the monograph below. The equivalent length is then added to the pipe length, and with this new pipe length the overall pipe friction loss is calculated. This method is rarely used today.

Erosion: The process in which a material is worn away by a stream of liquid (water) or air, often due to the presence of abrasive particles in the stream.

Estuary: A place where fresh and salt water mix, such as a bay, salt marsh, or where a river enters an ocean.

Evaporation: The process of liquid water becoming water vapor, including vaporization from water surfaces, land surfaces, and snow fields, but not from leaf surfaces. See transpiration.

Evapotranspiration: The sum of evaporation and transpiration.

Exemption: State or EPA permission for a water system not to meet a certain drinking water standard. An exemption allows a system additional time to obtain financial assistance or make improvements in order to come into compliance with the standard. The system must prove that: (1) there are compelling reasons (including economic factors) why it cannot meet a MCL or Treatment Technique; (2) it was in operation on the effective date of the requirement, and (3) the exemption will not create an unreasonable risk to public health. The state must set a schedule under which the water system will comply with the standard for which it received an exemption.

Expansion Tank: A small tank used in closed water heating systems and domestic hot water systems to relieve excess system pressure cause by the expansion of hot water. Modern-day expansion tanks feature a diaphragm that separates the hot water from the air cushion.

Expeller: A hydro-dynamic seal that provides a seal without addition of water to the gland, specially useful for liquid slurries.

Explosion Proof: A type of motor enclosure that resembles a TENV or TEFC motor with the added protection that the atmosphere cannot get into the motor and sparks in the motor cannot get out into the atmosphere.

Explosion-proo-1-f: Motor designed to withstand an internal explosion of gas or vapor and not allow flame or explosion to escape. Generally TEFC but also built TENV in smaller horsepower ratings. Motors are labeled to meet UL and NEC requirements.

External Gear pump: A positive displacement pump. Two spur gears are housed in one casing with close clearance. Liquid is trapped between the gear tooth spaces and the casing, the rotation of the gears pumps the liquid. They are also used for high pressure industrial transfer and metering applications on clean, filtered, lubricating fluids.

Extrol Expansion Tank: A brand of expansion tanks used in closed-loop hydronic and radiant heating systems.

Extrusion: Permanent displacement of a portion of the O-ring into a gap, under the action of fluid pressure.

Eye of the impeller: The center of the impeller, where the fluid enters.