Glossary of Groundwater and Water Well Terms


A condition in which water has a pH value of below 7.0.

Activated Carbon Filter

A type of filter utilizing porous carbon with a high surface area to trap organic chemicals and chlorine.


A condition in which water has a pH value of above 7.0.


An aquifer is a channel within (sand, gravel, sandstone, limestone, or bed rock) that will yield usable amounts of water to a well.

Artesian Water

Groundwater that is under pressure when tapped by a well and is able to rise above the level at which it is first found. It may or may not flow out at ground level. The pressure in an aquifer is artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer.


Unbroken solid rock, overlaid in most places by sailor rock fragments. In most wells, the well casing is driven into bedrock. Aquifers within the bedrock provide a water source for the well.


The hole drilled to construct a well. Most boreholes for domestic wells are slightly larger than the well casing until they reach bedrock, at which point they become slightly smaller than the well casing.

Capillary Action

The means by which liquid moves through the porous spaces in a solid, such as rocks, soil and plant roots.


Steel or plastic pipe placed in the borehole to keep it from collapsing. The casing is driven into the borehole wall to seal it off from surface water contamination.

Check Valve

A one way valve used in a pump system to} prevent the backflow of water once the system has been pressurized.


The act of disinfecting a well using chlorine or calcium chloride tablets.


The removal of salts from saline water to provide freshwater.


The volume of water that passes a given location within a defined period of time. It is usually expressed in gallons per minute.

Drainage Basin or Watershed

Land area where precipitation runs off into streams, rivers, lakes, reservoirs, or oceans.


The drawdown in a well is the difference between the pumping water level and the static non-pumping water level. Drawdown begins when the pump is turned on and increases as water is pumped.

Drop Pipe

The section of plastic or steel pipe inside a welt that connects the submersible pump or jet assembly to the pitless adapter.

Foot Valve

A type of check valve that is attached to the end of the drop pipe assembly in a shallow well pump system. Prevents backflow of water to the well while allowing the pump to draw water from the well.


Water that contains less than 1,000 milligrams per liter (mg/L) of dissolved solids. Generally, more than 500 mg/L of dissolved solids is undesirable for drinking and some industrial uses.

Gravel Well

A type of groundwater well where the casing is set in an unconsolidated mixture of rock fragments or pebbles.


Wastewater from clothes washing machines, showers, bathtubs, hand washing, lavatories, and sinks.


Water that flows or seeps downward saturating soil and rock aquifers. The upper surface of the saturated zone is called the water table.


A water-quality indicating the concentration of alkaline salts in water, mainly calcium and magnesium. If the water used is "hard" then more soap, detergent or shampoo is required to raise a lather.

Hydro fracturing

A type of well development in which water is injected into a low yield well at high pressure and volume in order to rupture water bearing fractures in bedrock to increase the yield.

Hydrologic Cycle

The cycle that begins with the evaporation of water mostly from the surface of the ocean, lakes, ponds, and rivers. As moist air is lifted, it cools and, water vapor condenses to form clouds. Moisture is then transported around the earth until It returns to the surface as precipitation.

Impermeable Layer

A layer of solid material, such as rock or clay, that does not allow water to easily pass through.


The controlled application of water for agricultural purposes through man-made systems to supply water requirements not satisfied by rain.

Jet Pump

A type of well pump that uses a special jet assembly to draw water up from the well. Shallow well jet pumps can draw water from a depth of up to 25 feet, while deep well jet pumps can pull water from a depth of 100 feet or more.

Leach Field

A network of perforated pipes that are laid in underground gravel-filled trenches to remove contaminants and impurities from the liquid that emerges from a septic tank.


The process by which soluble materials in the soil, such as salts, nutrients, pesticide chemicals, and contaminants, are washed into a lower layer of soil or are dissolved and carried away by water.

Maximum Demand

The heaviest amount of usage that a household will require from a well.


The movement of water molecules through a thin membrane. The osmosis process is one method of desalinating saline water.

Parts Per Billion (ppb)

The number of "parts" by weight of a substance per billion parts of water. It is used to measure extremely small concentrations.

Parts Per Million (ppm)

The number of "parts" by weight of a substance per million parts of water.


The ability of a material to allow the passage of a liquid, such as water, through rocks. Permeable materials, such as gravel and sand, allow water to move quickly through them, whereas impermeable material, such as clay, don't allow water to flow as freely.


A measure of the relative acidity or alkalinity of water. Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity, while pH levels higher than 7 indicate increasingly basic solutions.

Pressure Switch

A switch that connects the electrical service line from the breaker panel to the service line that supplies power to the well pump. The pressure switch senses the water pressure in the household plumbing and tells the pump to turn on (increase pressure) and off (reduce pressure) as needed.

Pressure Tank

A metal or fiberglass tank that stores water pressure in a pump system.

Pump System

The system that delivers water from a well to a house. A water pump moves the water the well to a tank inside the house, where it is stored under pressure. When the pressure inside the reaches a sufficient level the pressure switch shuts off the pump. As the water is remove from the tank during regular household use, the pressure switch turns the pump back on and the process is repeated as needed.

Pumping Water level

The pumping water level is the distance from the land surface to the water in the well while it is pumping.


Water added to an aquifer. For example, rainfall that seeps into the ground.

Reverse Osmosis Filter

A type of filter in which water passes through a porous semipermeable membrane to remove particles from drinking water. The process is usually preceded by a sediment filter and an activated carbon filter.

Rotary Drilling

A form of well drilling where a turning hammer assembly or a roller bit is incrementally lowered into the ground to create the borehole. A lifting agent is continually pumped through the hammer to remove drilling from the borehole. This can be comprised of an air and/or water mixture or an industrial drilling fluid.

Sanitary Seal

A well cap with a rubber gasket that provides a complete seal around the wellhead.

Saline Water

Water that contains significant amounts of dissolved solids, generally from 1,000 to 35,000 ppm.


A perforated material used to filter material such as sand from entering the wen pump.


A term usually applied to material in suspension in water or recently deposited from suspension.

Sediment Filter

A type of filter used to remove larger particulates from drinking water, such as rust and calcium carbonate.

Septic Tank

A tank used to detain domestic wastes to allow the settling of solids prior to distribution to a leach field for soil absorption. Septic tanks are used when a sewer line is not available to carry waste to a treatment plant.

Shallow Well Pump

A type of water pump that utilizes suction to draw water from a drop pipe assembly in the well. Limited to drawing water no more than 33.9 feet vertically, due to atmospheric pressure.


A water body formed when the side of a hill, a valley bottom or other excavation intersects a flowing body of groundwater at or below the local water table, below which the subsurface material is saturated with water.

Static water level

The static water level is the distance from the land surface to the water in the well under non-pumping or static conditions. Static water levels can be influenced by climatic conditions and pumping of nearby wells.

Submersible Pump

A type of well pump that is located in a borehole. A submersible pump can draw water from a much lower depth than a shallow well pump because it pushes the water up and out of the well rather than pulling it from the well at the surface level.

Suspended Solids

Solids that are not in true solution and that can be removed by filtration. Such suspended solids usually contribute directly to turbidity.

Torque Arrestor

An expandable rubber sleeve that attaches to the drop pipe above the pump to minimize the movement of the system when the pump turns on.


The amount of sediment or particles suspended in a liquid, such as water.

Water Cycle

The circuit of water movement from the oceans to the atmosphere and back to the Earth.

Water Line

The underground section of pipe that connects a well to the pressure tank inside a house or other building.

Water Quality

A term used to describe the chemical, physical, and biological characteristics of water, usually with respect to its suitability for a particular purpose such as drinking water.


The land area that drains water to a particular stream, river, lake or ocean.

Water table

The top of the saturated part of a water-table is an aquifer. Below the water table, pore spaces or fractures in rock and earthen materials are filled with water. Above the water table, the pore spaces are filled with air.

Water Well

A bored, drilled, or driven shaft, or a dug hole whose purpose is to reach underground water supplies.

Well Cap

A metal cover that fastens to the top of the wellhead, protecting the inside of the well from contamination.


The portion of the well that extends above the ground.

Well depth

The total depth of the well is the distance from the land surface to the bottom.

Well Storage

The volume of water in gallons contained in the well from the bottom of the well to the static water level.


The amount of water measured in gallons per minute that a well will produce when pumped.

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