Well Terminology

A list of terms and definitions.


Acidic: a condition in which the water in your well has a pH value of below 7.0. Highly acidic water can be problematic for your well system.


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


Alkaline: a condition in which the water in your well has a pH value of above 7.0. Highly alkaline water can be problematic for your well system.


Aquifer: An aquifer is a channel within a geologic formation (sand and gravel, sandstone, limestone, or other 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 encountered. It may or may not flow out at ground level. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer.


Arsenic (As): Arsenic is highly toxic and its prevalence is due to the natural occurrence of this metal and past use of arsenic in pesticides. Arsenic poisoning typically makes people feel tired and depressed and this poisoning is also associated with weight loss, nausea, hair loss, and marked by white lines across your toenails and fingernails. For freshwater the concentration should be less than 0.01 mg/L.


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


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


Cable Tool Drilling: A form of well drilling that is accomplished using a weighted string of drilling tools attached to hoisting cable that is repeatedly lifted and dropped. The force of the impact crushes the material at the bottom of the borehole. The crushed material is periodically cleared using a bailer.


Capillary Action: The means by which liquid moves through the porous spaces in a solid, such as soil, plant roots, and the capillary blood vessels in our bodies due to the forces of adhesion, cohesion, and surface tension.


Casing: 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.


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


Coliform Bacteria: Coliform bacteria are a type of bacteria that can re universally present in soil, aquatic environments, vegetation, and inside and on plants and animals. They are a commonly used indicator of water quality in domestic wells. While coliform are not normally dangerous, they can be an indicator of contamination of more serious pathogens.


Cut in pressure: The setting on the pressure switch that determines when the pump will turn on. The amount of air pressure in the pressure tank is typically set to 2 pounds below the cut in pressure.


Cut off pressure: The setting on the pressure switch that determines when the pump will turn off. Must be set high enough to prevent the pump system from short cycling, but low enough that the pressure tank will not rupture.


Desalination: The removal of salts from saline water to provide freshwater.


Discharge: The volume of water that passes a given location within a given period of time. Usually expressed in gallons per minute.


Drainage Basin: Land area where precipitation runs off into streams, rivers, lakes, and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins, like the area that drains into the Mississippi River contain thousands of smaller drainage basins. Also called a “watershed.”


Drawdown: 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 until the well reaches “steady state” sometime later.


Drop Pipe: The section of plastic or steel pipe inside the well 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 suck water from the well.


Freshwater: 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 many industrial uses.


Gravel Well: A type of water well where the casing is set in an unconsolidated mixture of rock fragments or pebbles.


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


Groundwater: Water that flows or seeps downward and saturates soil or rock, supplying springs and wells. The upper surface of the saturated zone is called the water table. Groundwater is stored underground in rock crevices and in the pores of geologic materials that make up the Earth’s crust.


Hardness: A water-quality indication of the concentration of alkaline salts in water, mainly calcium and magnesium. If the water you use is “hard” then more soap, detergent or shampoo is necessary to raise a lather.


Hydro fracturing: A type of well development in which water is injected into a low or no yield well at high pressure and volume in order to rupture water bearing fractures in bedrock and increase yield.


Hydrologic Cycle: The hydrologic cycle begins with the evaporation of water from the surface of the ocean. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported around the globe until it returns to the surface as precipitation.


Impermeable Layer: a layer of solid material, such as rock or clay, which does not allow water to pass through.


Irrigation: The controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall.


Iron Bacteria: A type of bacteria that feed on dissolved iron in well water. Although they are not a health hazard by themselves, the slime generated by iron bacteria can clog well system components and stain plumbing fixtures. Well chlorination can help prevent the growth of iron bacteria.


Jet Pump: A type of well pump that uses a special jet assembly to pull water up from the well.  Shallow well jet pumps can pull water from a depth of up to 25 feet, while deep well jet pumps can pull water from a depth of up to 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 the septic tank.


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


Maximum Contaminant Level (MCL)–the designation given by the U.S. Environmental Protection Agency (EPA) to water-quality standards promulgated under the Safe Drinking Water Act. The MCL is the greatest amount of a contaminant that can be present in drinking water without causing a risk to human health.


Maximum Demand: The heaviest amount of usage that a household will require from the well. This is critical factor in properly sizing the pump system.


Municipal Water System: A water system that has at least fifteen service connections or which regularly serves 25 individuals for 60 days; also called a public water system.


Osmosis: The movement of water molecules through a thin membrane. The osmosis process occurs in our bodies and is also one method of desalinating saline water.


Overburden: The rock / soil mixture that sits atop bedrock. Can be comprised of rock, clay, gravel, sand or soil. This is sealed off from the well by the well casing, except in the case of gravel wells, where the casing ends in the gravel formation.


Parts Per Billion (ppb): The number of “parts” by weight of a substance per billion parts of water. Used to measure extremely small concentrations.


Parts Per Million (ppm): The number of “parts” by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations.


Pathogen: A disease-producing agent; usually applied to a living organism. Generally, any viruses, bacteria, or fungi that cause disease.


Permeability: 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 unpermeable material, such as clay, don’t allow water to flow freely.


pH: 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.


Pitless Adapter: A below-grade fitting that connects the waterline to the drop pipe in the well. A quick disconnect mechanism allows for easy removal of a submersible pump from the well.


Pressure Switch: A switch that connects the electrical service line from the breaker panel to the service line that supplies power to the pump. The pressure switch senses the water pressure in the household plumbing and tells the pump to turn on (cut in pressure) and off (cut off pressure) accordingly.


Pressure Tank: A metal or fiberglass tank that stores water pressure in a pump system. Usually incorporates a vinyl bladder with pressurized air on one side and water on the other.


Public Water Supply: Water withdrawn by public governments and agencies, such as a county water department, and by private companies that is then delivered to users. Public suppliers provide water for domestic, commercial, thermoelectric power, industrial, and public water users. Most people’s household water is delivered by a public water supplier. The systems have at least 15 service connections (such as households, businesses, or schools) or regularly serve at least 25 individuals daily for at least 60 days out of the year.


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


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


Recharge: Water added to an aquifer. For instance, rainfall that seeps into the ground.


Reverse Osmosis Filter: A type of filter in which water passes through a porous semipermeable membrane to remove ions, molecules and larger particles from drinking water. Typically preceded by a sediment filter and an activated carbon filter to protect the membrane from harmful chemicals and particles.


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 drillings from the borehole.  This can be comprised of an air/water mixture, an industrial drilling fluid, or mud. Time required to drill a well is drastically reduced compared to cable tool methods.


Sanitary Seal: A well cap with a rubber gasket that provides a complete seal around the wellhead. Often used for buried wellheads or in conditions where contamination is likely.


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


Screen: A perforated material used to filter media such as sand from entering the well pump. Must be sized appropriately for the type of media to be filtered.


Sediment: Usually applied to material in suspension in water or recently deposited from suspension. In the plural the word is applied to all kinds of deposits from the waters of streams, lakes, or seas.


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 them to a treatment plant. A settling tank in which settled sludge is in immediate contact with sewage flowing through the tank, and wherein solids are decomposed by anaerobic bacterial action.


Shallow Well Pump: A type of water pump that utilizes suction to pull water from a drop pipe assembly in the well. Limited to pulling water no more than 33.9 feet vertically, due to atmospheric pressure. As these are only capable of working at shallower depths, they are commonly used to pull water from lakes or ponds for camps.


Spring: 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 (or the measuring point) to the water in the well under non-pumping (static) conditions. Static water levels can be influenced by climatic conditions and pumping of nearby wells and are often measured repeatedly to gain information about how aquifers react to climatic change and development.


Submersible Pump: A type of well pump that resides inside the 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 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.


Turbidity: The amount of sediment or particles suspended in liquid.


Water Cycle: The circuit of water movement from the oceans to the atmosphere and to the Earth and return to the atmosphere through various stages or processes such as precipitation, interception, runoff, infiltration, percolation, storage, evaporation, and transportation.


Water Line: The underground section of pipe that connects the well to the pressure tank inside the house.


Water Quality: A term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose (i.e. drinking water).


Watershed: The land area that drains water to a particular stream, river, or lake. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large watersheds, like the Mississippi River basin contain thousands of smaller watersheds.


Water table: The top of the saturated part of a water-table (also known as an unconfined) aquifer. Below the water table, pore spaces (or fractures) in the geologic media 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.


Wellhead: The portion of the well that extends above the ground.


Well depth: The total depth of the well is the distance from 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.


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