Users Guide to off Grid Energy Solutions
Glossary of Wells and Water Terminology
Terminology for wells and water is specific and technical. Some of the most important terms and concepts are supplied here for the reader courtesy of Dankoff Solar Products, Inc.
Driller's Log: The written form on which well characteristics are recorded by the well driller. In most states, drillers are required to register all water wells and to send a copy of the log to a state office. This supplies hydrological data and well performance test results to the public and to the well owner.
Drawdown: Lowering of level of water in a well due to pumping.
Recovery Rate: Rate at which groundwater refills the casing after the level is drawn down. This is the term used to specify the production rate of the well.
Static Water Level: Depth to the water surface in a well under static conditions (not being pumped). May be subject to seasonal changes or lowering due to depletion.
Wellhead: Top of the well, at ground level.
Cut-In Pressure and Cut-Out Pressure: See pressure switch.
Gravity Flow: The use of gravity to produce pressure and water flow. A storage tank is elevated above the point of use, so that water will flow with no further pumping required. A booster pump may be used to increase pressure. 2.31 Vertical Feet = 1 PSI. See pressure.
Head: See vertical lift and total dynamic head. In water distribution, synonym: vertical drop.
Open Discharge: The filling of a water vessel that is not sealed to hold pressure. Examples: storage (holding) tank, pond, flood irrigation. Contrast: pressure tank.
Pressure: The amount of force applied by water that is either forced by a pump, or by the gravity. Measured in pounds per square inch (PSI). PSI = vertical lift (or drop) in Feet / 2.31, or in bar (1 bar equals the equivalent downward force of a vertical shaft of water 10 metres high exerted on one square centimetre of surface).
Pressure Switch: An electrical switch actuated by the pressure in a pressure tank. When the pressure drops to a low set-point (cut-in) it turns a pump on. At a high point (cut-out) it turns the pump off.
Pressure Tank: A fully enclosed tank with an air space inside. As water is forced in, the air compresses. The stored water may be released after the pump has stopped. Most pressure tanks contain a rubber bladder to capture the air. If so, synonym: captive air tank.
Pressure Tank Pre-charge: The pressure of compressed air stored in a captive air pressure tank. A reading should be taken with an air pressure gauge (tire gauge) with water pressure at zero. The air pressure is then adjusted to about 3 PSI lower than the cut-in pressure (see Pressure Switch). If pre-charge is not set properly, the tank will not work to full capacity, and the pump will cycle on and off more frequently.
Permission to copy and distribute Glossary of Solar Water Pumping is herebygranted to all parties. Prior notification and citation of Copyright is required. A shortened version is also available. Copyright 1996 by Dankoff Solar Products, Inc.