Private Water Wells
If your family gets drinking water from a private well, do you know if your water is safe to drink? What health risks could you and your family face? Approximately 15% of Canadians rely on their own private drinking water supplies. Unlike public drinking water systems serving many people, they do not have experts regularly checking the water’s source and its quality before it is sent to the tap. These households must take special precautions to ensure the protection and maintenance of their drinking water supplies.
There are two typical types of private drinking water wells: dug and drilled. Proper well construction and continued maintenance are keys to the safety of your water supply. Your 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’s 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. Make certain your ground water contractor is registered or licensed if required.
To keep your well safe, you must be sure that possible sources of contamination are not close by. Experts suggest the following distances as a minimum for protection — farther are better
· septic tanks: 50 feet;
· livestock yards, silos, septic leach fields: 50 feet;
· petroleum tanks, liquid-tight manure storage and fertilizer storage and handling: 100 feet; and
· manure stacks: 250 feet.
Many homeowners tend to forget the value of good maintenance until problems reach crisis-levels. That can be expensive. It’s better to maintain your well, find problems early, and correct them to protect your well’s performance. Keep up-to-date records of well installation and repairs, plus pumping and water tests. Such records can help spot changes and possible problems with your water system. If you have problems, ask a local expert to check your well construction and maintenance records. He or she can see if your system is okay or needs work.
Dug wells are holes in the ground dug by shovel or backhoe. Historically, a dug well was excavated below the ground water table until incoming water exceeded the digger’s 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 pre-cast concrete), and a cement grout or bentonite clay sealant poured along the outside of the casing to the top of the well.
· The well should be covered by a concrete curb and 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.
Land activities around a dug well can also contaminate it. While dug wells have been used as a household water supply source for many years, most are relics 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.
Drilled wells penetrate about 100 to 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, 6 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 5 feet extending into the bedrock. The casing should also extend a foot or two above the ground’s 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 should be 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 province.
· The well pipe used was often 8, 10 or 12 inches in diameter, and covered with a concrete well cap either at or below the ground’s surface. This outmoded type of construction does not provide the same degree of protection from surface contamination.
How can I test the quality of my private drinking water supply?
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 area with no sewers.