Photograph of  a loose, unsanitary well plumbing system exposed to surface water runoffr  © DJ Friedman Definitions of Terms used with Drinking Water & Wells

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An Illustrated Water Well Terminology Dictionary: EPA & other definitions of drinking water, well, and well contamination terms.

This article gives you general information about drinking water from home wells (also considered private drinking water sources).

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Definitions - of Terms Describing Drinking Water from Household Wells

Dug well (C) 2012 2013 DanieL Friedman Tlaxcala MexicoAquifer - An underground formation or group of formations in rocks and soils containing enough ground water to supply wells and springs.

Backflow - 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. Also called back siphonage.

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.

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 between a water softener drain line and a sewer line (C) InspectApedia

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

Our photo (left) shows a water softener drain line connected to a sewer line. Sewage backup can easily enter the water softner brine tank through this connection, risking contaminating the building water supply.

Dug well - any hand-excavated (or in some cases machine excavated) shallow well, such as shown above, intended for use as a water source. See DUG WELLS, by HAND for details.

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.

Leaching field - The entire area where many materials (including contaminants) dissolve in rain, snowmelt, or irrigation water and in most common instances, onsite wastewater effluent disposal areas ore septic drainfields are filtered through the soil. Synomyms for leaching field are leach field, drainfield, soakaway bed, seepage bed and similar terms. Details are at SEPTIC DRAINFIELD INSPECTION & TEST.

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.

Protozoa - One-celled animals, usually microscopic, that are larger and more complex than bacteria. May cause disease.

Radon in water treatment system  (C) InspectApedia

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.

Shown at left is a system for removing radon gas from drinking water. Details about radon testing and radon gas level correction systems in buildings are at RADON HAZARD TESTS & MITIGATION.

Radionuclides - 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.

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 - The land area that catches rain or snow and drains it into a local water body (such as a river, stream, lake, marsh, or aquifer) and affects its flow, and the local water level. Also called a recharge area.

Well cap - Two Harbors MN (C) 2011 2013 DanieL FriedmanWater table - The upper level of the saturated zone. This level varies greatly in different parts of the country and also varies seasonally depending on the amount of rain and snowmelt.

Water well: an opening dug, drilled, or otherwise made into the soil intended to obtain and provide water for drinking, animal use, or other processes. A water well receives its water supply from groundwater, a spring, or similar sources. Types of water wells are detailed at WELLS CISTERNS & SPRING.

Well cap - A tight-fitting, vermin-proof seal designed to prevent contaminants from flowing down inside of the well casing. Well caps are installed atop a steel well liner or casing, typical 6" in diameter but also available in smaller & larger sizes for water wells.

Our photo illustrates a new well cap (orange arrow) installed atop a steel well casing in Two Harbors, MN. You can see by the plastic electrical conduit that this well is served by a submersible well pump.

The red-tipped stake by the well casing is intended to mark the well location when there is snow cover, in hope that the snow plow, when pushing snow off of the driveway, won't smash the well casing.

Well cover - a tight-fitting, secure safety cover installed atop a dug well or well pit both to keep out animals or vermin and as a safety device to prevent someone from falling into the opening. We discuss well covers for wells & well pits further at WELL PITS.

Well cover on a dug well in Tlaxcala, Mexico (C) 2013 Daniel Friedman

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

Steel well casing, no cap (C) InspectApedia ApplemarkIn our photo at left, what appears to be a ten-inch steel drilled well casing has no cap, suggesting that this well is either not in use or is not properly installed.









Well pit - an opening in the ground housing the top of a well casing or other well type and sometimes additional well equipment including pumps, pressure tanks, and electrical controls.

Photograph of a water well pit

A well pit is intended to protect well piping and components from freezing in cold climates where those components must be located outside of the building(s) served by the well.

Our photo (above left) shows a dangerous well pit that is collapsing and that lacks a safety cover.

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


Continue reading at CONSULT LOCAL WELL EXPERTS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



EPA GUIDE to WATER QUALITY - annotated, illustrated & expanded guide to Ground water & Well Contamination


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WELL & WELL WATER DEFINITIONS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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