Definitions and Terms

DRAWDOWN
The distance that the water level in the well is lowered by pumping. It is the difference between the STATIC WATER LEVEL and the PUMPING LEVEL.

ELEVATION
The vertical distance between the level where fluid enters a pipe and the level where it leaves. It 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.

FRICTION LOSS
The loss of pressure or head due to the resistance to flow in the pipe and fittings. Friction loss is influenced by pipe size and fluid velocity, and is usually expressed in feet of head.

HORIZONTAL RUN
The horizontal distance between the point where fluid enters a pipe and the point at which it leaves.

PUMPING LEVEL
The lowest water level reached during pumping operation.

SERVICE PRESSURE
The range of pressure in the pressure tank during the pumping cycle, usually expressed in pounds per square inch gauge (P.S.I.G.).

SETTING
The vertical distance from the level at which the discharge pipe leaves the well to the bottom of the pump or jet assembly in the well.

STATIC OR STANDING WATER LEVEL
The undisturbed level of water in the well before pumping.

SUBMERGENCE
The vertical distance between PUMPING LEVEL and the bottom of the pump or jet assembly. Submergence must be sufficient to insure that the suction opening of the pump or jet assembly is always covered with water, while maintaining enough clearance from the bottom of the well to keep it out of sediment (at least 10 feet clearance is recommended).

TOTAL DISCHARGE HEAD
The total pressure or head the pump must develop. It is the sum of the depth to PUMPING LEVEL, THE ELEVATION, THE SERVICE PRESSURE, and THE FRICTION LOSS. Of course, all of these measurements must be expressed in the same units, usually feet of head, before adding them together.