Drinking Water Wells

Frequently Asked Questions

There are three types of private drinking water wells: dug, driven, and drilled. See the three links below for an explanation and graphic of the types of wells.

* Dug Wells
* Driven Wells
* Drilled Wells

Overview
Proper well construction and continued maintenance are keys to the safety of your water supply. Your state water-well contractor licensing agency, local health department, or local water system professional can provide information on well construction.

The well should be located so rainwater flows away from it. Rainwater can pick up harmful bacteria and chemicals on the land’Äôs surface. If this water pools near your well, it can seep into it, potentially causing health problems.

Water-well drillers and pump-well installers are listed in your local phone directory. The contractor should be bonded and insured. Make certain your ground water contractor is registered or licensed in your state, if required. If your state does not have a licensing/registration program contact the National Ground Water Association. They have a voluntary certification program for contractors. (In fact, some states use the Association’Äôs exams as their test for licensing.)

DUG WELLS

Dug wells are holes in the ground dug by shovel or backhoe. Historically, a dug well was excavated below the groundwater table until incoming water exceeded the digger’Äôs bailing rate. The well was then lined (cased) with stones, brick, tile, or other material to prevent collapse. It was covered with a cap of wood, stone, or concrete. Since it is so difficult to dig beneath the ground water table, dug wells are not very deep. Typically, they are only 10 to 30 feet deep. Being so shallow, dug wells have the highest risk of becoming contaminated.To minimize the likelihood of contamination, your dug well should have certain features. These features help to prevent contaminants from traveling along the outside of the casing or through the casing and into the well.

Dug Well Construction Features

* The well should be cased with a watertight material (for example, tongue-and-groove precast concrete) and a cement grout or bentoniteclay sealant poured along the outside of the casing to the top of the well.
* The well should be covered by a concrete curband cap that stands about a foot above the ground.
* The land surface around the well should be mounded so that surface water runs away from the well and is not allowed to pond around the outside of the wellhead.
* Ideally, the pump for your well should be inside your home or in a separate pump house, rather than in a pit next to the well.

While dug wells have been used as a household water supply source for many years, most are ’Äúrelics’Äù of older homes, dug before drilling equipment was readily available or when drilling was considered too expensive. If you have a dug well on your property and are using it for drinking water, check to make sure it is properly covered and sealed. Another problem relating to the shallowness of a dug well is that it may go dry during a drought when the ground water table drops.

DRIVEN WELLS

Like dug wells, driven wells pull water from the water-saturated zone above the bedrock. Driven wells can be deeper than dug wells. They are typically 30 to 50 feet deep and are usually located in areas with thick sand and gravel deposits where the ground water table is within 15 feet of the ground’Äôs surface. In the proper geologic setting, driven wells can be easy and relatively inexpensive to install. Although deeper than dug wells, driven wells are still relatively shallow and have a moderate-to-high risk of contamination from nearby land activities.

Driven Well Construction Features

* Assembled lengths of two inches to three inches diameter metal pipes are driven into the ground. Ascreened ’Äúwell point’Äù located at the end of the pipe helps drive the pipe through the sand and gravel. The screen allows water to enter the well and filters out sediment.
* The pump for the well is in one of two places: on top ofthe well or in the house. An access pit is usually dug around the well down to the frost line and a water dis-charge pipe to the house is joined to the well pipe with a fitting.
* The well and pit are capped with the same kind of large-diameter concrete tile used for a dug well. The access pit may be cased with pre-cast concrete.

To minimize this risk, the well cover should be a tight-fitting concrete curb and cap with no cracks and should sit about a foot above the ground. Slope the ground away from the well so that surface water will not pond around the well. If there’Äôs a pit above the well, either to hold the pump or to access the fitting, you may also be able to pour a grout sealant along the outside of the well pipe. Protecting the water quality requires that you maintain proper well construction and monitor your activities around the well. It is also important to follow the same land use precautions around the driven well as described under dug wells.

DRILLED WELLS

Drilled wells penetrate about 100-400 feet into the bedrock. Where you find bedrock at the surface, it is commonly called ledge. To serve as a water supply, a drilled well must intersect bedrock fractures containing ground water.

Drilled Well Construction Features

* The casing is usually metal or plastic pipe, six inches in diameter that extends into the bedrock to prevent shallow ground water from entering the well. By law, the casing has to extend at least 18 feet into the ground, with at least five feet extending into the bedrock. The casing should also extend a foot or two above the ground’Äôs surface. A sealant, such as cement grout or bentonite clay, should be poured along the outside of the casing to the top of the well. The well is capped to prevent surface water from entering the well.
* Submersible pumps, located near the bottom of the well, are most commonly used in drilled wells. Wells with a shallow water table may feature a jet pump located inside the home. Pumps require special wiring and electrical service. Well pumps should be installed and serviced by a qualified professional registered with your state.
* Most modern drilled wells incorporate a pitless adapter designed to provide a sanitary seal at the point where the discharge water line leaves the well to enter your home. The device attaches directly to the casing below the frost line and provides a watertight subsurface connection, protecting the well from frost and contamination.
* Older drilled wells may lack some of these sanitary features. The well pipe used was oftene ight-, 10- or 12- inches in diameter, and covered with a concrete well cap either at or below the ground’Äôs surface. This outmoded type of construction does not provide the same degree of protection from surface contamination. Also, older wells may not have a pitless adapter to provide a seal at the point of discharge from the well.

Hydrofracting A Drilled Well

Hydrofracting is a process that applies water or air under pressure into your well to open up existing fractures near your well and can even create new ones. Often this can increase the yield of your well. This process can be applied to new wells with insufficient yield and to improve the quantity of older wells.

FREQUENTLY ASKED QUESTIONS

* How can I test the quality of my private drinking water supply?
* What concerns should I have after a flood if I have a private well?
* How can I protect my private water supply?

How can I test the quality of my private drinking water supply?¬Ý

Consider testing your well for pesticides, organic chemicals, and heavy metals before you use it for the first time. Test private water supplies annually for nitrate and coliform bacteria to detect contamination problems early. Test them more frequently if you suspect a problem. Be aware of activities in your watershed that may affect the water quality of your well, especially if you live in an unsewered area.

Reasons to Test Your Water

Recurring gastro-intestinal illness (Test for: Coliform bacteria)
Household plumbing contains lead (Test for: pH, lead, copper)
Radon in indoor air or region is radon rich (Test for: Radon)
Corrosion of pipes, plumbing (Test for: Corrosion, pH, lead)
Nearby areas of intensive agriculture (Test for: Nitrate, pesticides, coliform bacteria)
Coal or other mining operations nearby (Test for: Metals, pH, corrosion)
Gas drilling operations nearby (Test for: Chloride, sodium, barium, strontium)
Dump, junkyard, landfill, factory, gas station, or dry-cleaning operation nearby (Test for: Volatile organic compounds, total dissolved solids, pH, sulfate, chloride, metals)
Odor of gasoline or fuel oil, and near gas station or buried fuel tanks (Test for: Volatile organic compounds)
Objectionable taste or smell (Test for: Hydrogen sulfide, corrosion, metals)
Stained plumbing fixtures, laundry (Test for: Iron, copper, manganese)
Salty taste and seawater, or a heavily salted roadway nearby (Test for: Chloride, total dissolved solids, sodium)
Scaly residues, soaps don’Äôt lather (Test for: Hardness)
Rapid wear of water treatment equipment pH, corrosion
Water softener needed to treat hardness (Test for: Manganese, iron)
Water appears cloudy, frothy, or colored (Test for: Color, detergents)

If you use a private laboratory to conduct the testing, nitrate and bacteria samples will typically cost between $10 and $20 to complete. Testing for other contaminants will be more expensive. For example, testing for pesticides or organic chemicals may cost from several hundred to several thousand dollars.¬ÝOnly use laboratories that are certified to do drinking water tests.

* A State Certification Officer to get a list of certified water testing labs in your state.
* Your local health department may also test private well water for free. Phone numbers for your local, county, or state health department are available under the "health" or "government" listings in your phone book.

Most laboratories mail back the sample results within a week or two. If a contaminant is detected, the results will include the concentration found and an indication of whether this level exceeds a drinking water health standard.

If a standard is exceeded in your sample, retest the water supply immediately and contact your public health department for assistance. Some problems can be handled quickly. For example, high bacteria concentrations can sometimes be controlled by disinfecting a well. Filters or other on-site treatment processes may also remove some contaminants. Other problems may require a new source of water, or a new, deeper well. If serious problems persist, you may need to rely on bottled water until a new water source can be obtained.

You should test private water supplies annually for nitrates,coliform bacteria, total dissolved solids, and pH levels to detect contamination problems early. Test more frequently if a problem was found in earlier tests.

What concerns should I have after a flood if I have a private well?

* Stay away from the well pump while flooded to avoid electric shock.
* Do not drink or wash from the flooded well to avoid becoming sick.
* Get assistance from a well or pump contractor to clean and turn on the pump.
* After the pump is turned back on, pump the well until the water runs clear to rid the well of flood water.
* If the water does not run clear, get advice from the county or state health department or extension service.

For additional information: "What to Do After the Flood" and "Disinfecting Wells" - From the Center for Disease Control

How can I protect my private water supply?

Protect your water supply by carefully managing activities near the water source. For households using a domestic well, this includes keeping contaminants away from sinkholes and the well itself. Keep hazardous chemicals out of septic systems.

* Periodically inspect exposed parts of the well for problems such as:
* cracked, corroded, or damaged well casing
* broken or missing well cap
* settling and cracking of surface seals.

* Slope the area around the well to drain surface runoff away from the well.
* Install a well cap or sanitary seal to prevent unauthorized use of, or entry into, the well.
* Have the well tested once a year for coliform bacteria, nitrates, and other constituents of concern.
* Keep accurate records of any well maintenance, such as disinfection or sediment removal, that may require the use of chemicals in the well.
* Hire a certified well driller for any new well construction, modification, or abandonment and closure.
* Avoid mixing or using pesticides, fertilizers, herbicides, degreasers, fuels, and other pollutants near the well.
* Do not dispose of wastes in dry wells or in abandoned wells.
* Do not cut off the well casing below the land surface.
* Pump and inspect septic systems as often as recommended by your local health department.
* Never dispose of harsh chemicals, solvents, petroleum products, or pesticides in a septic system or dry well.

The information contained on this page were provided by The Rhode Island Department of Environmental Management and the U.S. Environmental Protection Agency.