Drinking water sources include surface water and ground water. Ground water is usually a safer drinking water source, but contamination to ground water supplies can occur. To keep your drinking water safe, wells should be regularly inspected, maintained, and tested for bacterial contamination. Additional information on the types of water sources for private water supplies is below.
Surface Water
Surface water is any source of water that is open to the atmosphere and is subject to runoff from the land. This includes lakes, streams, rivers, ponds and springs. Because these sources are open to the environment and subject to runoff, it is likely that the water will contain micro-organisms such as bacteria, viruses and parasites that can cause illness.
Surface water must be properly treated with filtration and disinfected before drinking it.
Well Types
Drilled well
A drilled well consists of a hole bored into the ground using a drilling rig and the upper part is lined with a casing. The casing protects the groundwater source, provides a housing for the pumping equipment and is the wall of the well which protects it from contamination and cave-ins. Most drilled wells reach deep aquifers, and have a lower risk for contamination and more constant temperature. However, they can be vulnerable to deep aquifer contaminants and can have poorer natural water quality (e.g., salt).
Dug Well
A dug well is a hole in the ground dug by a shovel or backhoe. Dug wells are used when water is close to the surface. The well is usually lined with a concrete casing to prevent collapse and then covered with a concrete cap. Dug wells are not very deep, typically reaching only 10 to 30 feet below ground. Water temperature can change seasonally. These shallow wells have a higher risk for contamination with bacteria.
Driven Point Well
A driven point well, also called a sand point well, is normally constructed in sand and gravel. They are small in diameter well made with steel pipes that are threaded together with a well screen at the end which is usually 2 to 3 feet long. The purpose of the screen is to allow groundwater to follow into the well but keep the surrounding sand out. These wells access a shallow water table so they tend to have limited yield and possible water shortages in dry periods. They are also more vulnerable to contamination with bacteria.
Well Disinfection
You should disinfect your well when:
- test results show it is contaminated
- after a flood
- a new well is installed
- after repairs or maintenance
- the well pump is serviced
Details on how to disinfect your well are available in the well disinfection tool developed by Public Health Ontario.
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