Source water

Wells must be a safe distance from pollution sources, have a water-tight casing and be protected overall from contaminants

Preventing drinking water contamination at the source can be accomplished by identifying contaminants of concern and reducing or eliminating them. Water can become contaminated with: biological organisms, such as bacteria, parasites and viruses chemical agents, such as nitrates and lead toxins created by algae in surface water

Types of source water

Secure ground water systems

A secure ground water system is a well system that is designed and maintained in accordance with Regulation 903 – Wells under the Ontario Water Resources Act. Important considerations are that the well is a safe distance from any pollution source, has a water-tight casing to over 6 metres in depth and is otherwise protected from surface water contamination.

A secure groundwater system without treatment may be capable of providing safe water. If no treatment is provided, ensuring the safety of the water is limited to source water protection and routine surveillance activities.

Some tips to prevent contamination of your secure ground water supply:

Non-secure ground water systems

A non-secure groundwater system is a well or other groundwater collection system that is not a safe distance from pollution sources or is not designed or constructed to prevent contamination by surface water.

If you get your drinking water from a well, contaminants may enter through cracks in the casing, poorly fitted lids or other structural faults. Private wells can become contaminated with bacteria, nitrates or other chemicals if they are close to sources of pollution.

A non-secure groundwater source will require disinfection, at a minimum, to be used for drinking water. This type of water supply has a greater potential for becoming contaminated. The treatment equipment must be checked and maintained to ensure proper operation.

Some tips to prevent contamination of non-secure ground water supply:

Surface water systems

A surface water system is any system that draws water from surface water or a system that may be contaminated by surface water.

Surface water sources are unsafe for drinking, unless the water is filtered and treated to destroy harmful micro-organisms. A surface water system (which may also include a groundwater system that is contaminated by surface water) requires both filtration to physically remove microbes that are not killed by disinfection and disinfection to kill bacteria and viruses.

Some tips to prevent contamination of a surface water supply:

Factors that affect source water quality

Protect the source(s) of drinking water from contamination and overuse to support the provision of safe, clean drinking water.

Preventing drinking water contamination at the source can be accomplished by identifying contaminants of concern and reducing or eliminating them. Potential sources of contamination include:


This item was last modified on November 20, 2015