Domestic Water Systems Terminology

Acceptance Factor Tank drawdown expressed in percentage. Example: The acceptance factor of a bladder tank with a pressure setting of 30/50 PSI is 31% (.31).

Air Volume Control Maintains the air charge in a standard water storage tank. Pre-charged tanks do not require an air volume control.

Average discharge pressure Usual average discharge pressure is 40 PSI - halfway between the 30-50 PSI pressure switch setting of most water systems. When the tank is installed away from the pump at a higher level, or when house or yard fixtures are above the pump and tank, a greater pressure is needed and a larger pump must be used.

Capacity Amount pumped in gallons per minute or gallons per hour, etc. The pump should have enough capacity so that it does not need to work more than the equivalent in intermittent service of 2 hours per day.

Check valve A one way valve placed in-line in the suction pipe to prevent water from falling back into the well, resulting in loss of prime.

Cistern An undergroumd tank built to collect water from wells or act as a storage for future use.

Discharge Head The difference in elevation between the liquid level of the discharge tank and the centerline of the pump. This head also includes any additional pressure head that may be present at the discharge tank fluid surface.

Drawdown (tank) The amount of water that can be removed from a tank, when it is full, before the tank pressure drops and the pump is turned on to refill the tank. A larger tank gives more drawdown which means that more water is available before the pump is needed.

Drawdown (well) The distance the water level drops below the standing water level while the pump is operating.

Drive water In a jet pump, the water which is supplied under pressure to drive the jet.

Dynamic Discharge Head The Static Discharge Head plus the friction in the discharge line. Also referred to as Total Discharge Head.

Ejector An assembly containing a nozzle and venturi which is used to draw water from a well in conjunction with a centrifugal pump. Same as injector.

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.

Fixture count A method of establishing the required number of gallons per minute to satisfy water needs by counting the number of water-fixtures in a home, where one fixture equals 1 GPM.

Foot valve A screened check valve used at the end of the suction pipe to prevent dirt and debris from clogging the pump and maintain prime.

Friction loss The loss of pressure expressed in feet (head) caused by the turbulence created in water while traveling through the pipe. To express pressure in feet, multiply by 2.31.

GPM/GPH Used to express the number of gallons per minute or gallons per hour produced by a pump or capacity requirements for residential usage.

Ground water Surface water that seeps down through the earth and accumulates in porous material at subsurface level.

Head Head is pressure expressed in terms of height in feet. 1 PSI X 2.31 = head in feet; 1 foot of water X .433 = 1 PSI

Hermetic Completely sealed, especially against the escape or entry of air

Impeller The rotating element of a pump which imparts movement and pressure to a fluid.

Injector An assembly containing a nozzle and venturi which is used to draw water from a well in conjunction with a centrifugal pump. Same as injector. Same as ejector.

Jet pump A centrifugal pump incorporating an ejector assembly.

Minimum run time The minimum length of time that the pump should run while refilling the pressure tank. At least 1 minute run time is recommended.

PSI Pressure expressed in pounds per square inch.

Potable water Water that is suitable for drinking.

Pre-Charged Tank A water storage tank pre-charged with air at factory featuring a vinyl bag to separate water from air which prevents waterlogging. This tank design provides greater drawdown than standard tanks. Pre-charged tanks do not require air volume control.

Pumping Cycles The times that a pump turns on and off.

Pumping level The vertical distance in feet from the pump to the water level while the pump is operating.If the pump is installed away from the well and is on higher ground, this elevation must also be included. Most wells draw down while being pumped so this must not be confused with the standing water level.

Service pressure The pressure required at the outlets. (Expressed in PSI.) The most commonly used discharge pessure is 30/50 PSI.

Setting for Pumps: vertical distance in feet from the top of the well to the top of the pump.

Settings for Foot valve or strainer: Vertical distance in feet from the top of the well to the top of the foot valve or strainer.

Standing water level The distance from the top of the well to the top of the water when the pump is not running.

Static discharge head The vertical distance from the pump to the highest outlet in the water system.

Static water level Vertical distance from the top of the well to the standing natural water level. Also known as "standing water level" and as "the water table".

Submergence The distance the ejector, foot valve or submersible pump is installed below the pumping level.

Submersible well pump ( 4") A submersible pump consists of two components, a pump end and a submersible motor. The motor end consists of several impellers and diffusers (called stages) that spin on a common shaft. The number of stages determines the head (or pressure) the pump will develop. 4" indicates that the pump will fit a minimum 4" inside diameter well casing.

Surface water Naturally occurring water from rainfall which creates lakes, rivers and streams.

Tail pipe The pipe added below the jet assembly, in a weak well application. (See weak well)

Total Dynamic Head (TDH) The Dynamic Suction Head plus the Dynamic Discharge Head. Also referred to as Total Head. Total Dynamic Head (TDH) is the total equivalent height that a fluid is to be pumped, taking into account friction losses in the pipe. TDH is simply the pressure head difference between the inlet and outlet of the pump, if measured at the same elevation and with inlet and outlet of equal diameter. TDH = Static Height + Static Lift + Friction Loss......where:

Static Height is the maximum height reached by the pipe after the pump (also known as the 'discharge head').

Static Lift is the height the water will rise before arriving at the pump (also known as the suction head).

Friction Loss (or Head Loss). The Dynamic Suction Head plus the Dynamic Discharge Head. Also referred to as Total Dynamic Head (TDH).

Total Suction Lift Total Suction Lift = Vertical Lift + Friction loss. Total Suction Lift is also called "Suction Conditions"

Vertical Lift The distance between the pumping level of the well and the center line of the pump, expressed in feet.

Water wells Generally classified according to the method used to create or construct the well. The four most common types are dug wells, bored wells, driven wells and drilled wells.

Weak wells A weak well application occurs when the pump lowers the water level in the well faster than the well can replenish itself. A deep well jet pump with a tail pipe is particularly effective when flow requirements are relatively small. By adding 35 feet of tail pipe below the jet assembly with a foot valve attached at the bottom, it will not be possible to pull the well down and allow air to enter the system.

Well casing A steel or plastic pipe inserted into a drilled well to prevent dirt and debris from contaminating the water.

Well (deep) A well with a static (standing) water level greater than 25'.

Well (shallow) A well with a static (standing) water level of 25' or less.

Well size The inside diameter of the well.

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