Domestic Water Well Definitions

Annular seal - when a well is drilled, the hole in the ground is larger than the well casing. This gap, the annular space, is filled with a water tight sealant, usually bentonite. Bentonite does not crack or shrink in the ground. Regulation 903 prescribes the minimum depth of the sealant.

Aquifer - An underground formation or group of formations in rocks and soils containing enough ground water to supply wells and springs.

Backflow - Also called back siphonage, a reverse flow in water pipes. A difference in water pressures pulls water from sources other than the well into a home’s water system. For example, waste water or flood water.

Bacteria - Microscopic living organisms; some are helpful and some are harmful. “Good” bacteria aid in pollution control by consuming and breaking down organic matter and other pollutants in septic systems, sewage, oil spills, and soils. However, “bad” bacteria in soil, water, or air can cause human, animal, and plant health problems.

Coliform bacteria - a group of bacteria predominaantly inhabiting the intestines of humans or animals but occasionaly found elsewhere. The presence of this bacteria in water is used as an indication of fecal contamination. (contamination by human or animal waste)

Confining layer - Layer of rock that keeps the ground water in the aquifer below it under pressure. This pressure creates springs and helps supply water to wells.

Contaminant - Anything found in water (including microorganisms, minerals, chemicals, radionuclides, etc.) which may be harmful to human health.

Cross-connection - Any actual or potential connection between a drinking (potable) water supply and a source of contamination.

Heavy metals - Metallic elements with high atomic weights, such as, mercury chromium cadmium, arsenic, and lead. Even at low levels these metals can damage living things. They do not break down or decompose and tend to build up in plants, animals, and people causing health concerns.

Hydrologic cycle - is the natural process of rain and snow falling to earth and evaporating back to form clouds and fall again. The water falling to earth flows into streams, rivers, lakes and into the soil collecting to form groundwater.

Leaching field - The entire area where many materials (including contaminants) dissolve in rain, snowmelt, or irrigation water and are filtered through the soil.

Microorganisms - Also called microbes. Very tiny life forms such as bacteria, algae, diatoms, parasites, plankton, and fungi. Some can cause disease.

Nitrates - Plant nutrient and fertilizer that enters water supply sources from fertilizers, animal feed lots, manures, sewage, septic systems, industrial wastewaters, sanitary landfills, and garbage dumps.

Nitrogen, in the forms of nitrate, nitrite, or ammonium, is a nutrient needed for plant growth. About 78% of the air that we breathe is composed of nitrogen gas. Some forms of nitrogen are commonly deposited in acid rain. Although nitrogen is abundant naturally in the environment, it is also introduced through sewage and fertilizers.

Phosphorus - is an essential element for plant life, but when there is too much of it in water, it can speed up eutrophication (a reduction in dissolved oxygen in water bodies caused by an increase of mineral and organic nutrients) of rivers and lakes.

Protozoa - small single-cell animals, usually microscopic, that are larger and more complex than bacteria. (including amoebas, ciliates and flagelates)

Radon - A colorless, odorless naturally occurring radioactive gas formed by the breakdown or decay of radium or uranium in soil or rocks like granite. Radon is fairly soluble in water, so well water may contain radon.

Radionuclides - a material with an unstable atomic nucleous that spontaneously decays or disintegrates producing radiation. Distinct radioactive particles coming from both natural sources and human activities. Can be very long lasting as soil or water pollutants.

Recharge area - The land area through or over which rainwater and other surface water soaks through the earth to replenish an aquifer, lake, stream, river, or marsh. Also called a watershed.

Runoff - that part of the precipitation or snow melt water that appears in uncontrolled surface streams, rivers, drains or sewers. Runoff may be classified according to speed of appearance after rainfall or melting snow as direct runoff or base runoff, and according to source as surface runoff, storm interflow, or ground-water runoff.

Saturated zone - The underground area below the water table where all open spaces are filled with water. A well placed in this zone will be able to pump ground water.

Unsaturated zone - The area above the ground water level or water table where soil pores are not fully saturated, although some water may be present.

Viruses - Submicroscopic disease-causing organisms that grow only inside living cells.

Watershed - is the land area where water soaks through the earth filling an underground water supply or aquifer. It is also called a recharge area.

Water table - is the line below which the ground is saturated or filled with water and available for pumping. The water table will fall during dry seasons. A well can pump water from either the saturated zone or an aquifer. Wells must be deep enough to remain in the saturated zone.

Well cap - A tight-fitting, vermin-proof seal designed to prevent contaminants from flowing down inside of the well casing.

Well casing - The tubular lining of a well. Also a steel or plastic pipe installed during construction to prevent collapse of the well hole.

Wellhead - The top of a structure built over a well. Term also used for the source of a well or stream.

Well pit - common on wells contstructed before 1985, the well casing was terminated below ground and an access pit such as well tiles were placed over and around the casing with a lid. This was done to protect the water lines from freezing.