The Quality of My Well Water

Développement durable, Environnement et Parcs

The Quality of My Well Water

Water is a resource that is both invaluable and vital. As the owner of an individual well or waterworks system serving less than 21 persons, you are responsible for ensuring its quality with a view to protecting your health and that of your loved ones. In this document, you will find all the information you need to meet this obligation.

Other Document

List of accredited laboratories (French)

Wells (French)

The quality of my well water and my responsibilities
Microbiological indicators of water quality
Presence of E. coli or enterococcal bacteria in my water
Presence of total coliforms in my water
Determining the source of contamination
The quality of my well water during a flood
Quantity of bleach required to disinfect a well
- Calculation tool
Nitrates/nitrites
My water still does not meet the quality standards…
Having my water tested..
For more information

The quality of my well water and my responsibilities

Whether water that is intended for consumption comes from a surface well or a cased well (commonly known as an "artesian well"), it must be of good quality and meet the standards set out in the Regulation respecting the quality of drinking water. Owners of individual wells or waterworks systems (serving less than 21 persons) are responsible for ensuring the quality and safety of the drinking water they provide.

While well water may appear to be clear and pure, and have no specific odor or taste, it may contain elements that can have undesirable effects on health, for example pathogenic micro-organisms (bacteria, viruses, or protozoa) and nitrates/nitrites.

Groundwater, which is generally of better quality than surface water (lakes, rivers, streams) owing to the soil’s natural filtering capacity, may be vulnerable to contamination, and precautions must be taken to ensure a supply of good quality water at all times.

Ministère du Développement durable, de l’Environnement et des Parcs (MDDEP) recommends that water be tested at least twice a year, namely in the spring and fall. Additional tests should be performed if you notice sudden changes in the water’s taste, odor, or appearance, or if changes have been made to the well or surrounding soil. These tests should be carried out by an accredited laboratory.

Water testing alone cannot guarantee drinking water quality. In addition to the recommended tests, you must check the condition of the well and septic facilities, examine possible sources of contamination in the environment around the well, and take the appropriate remedial measures. The document Le puits presents the design standards that must be met for three types of well (artesian wells, surface wells, and sand-point wells).

When setting up a new well, you are obliged by the regulation to carry out certain tests, including Escherichia coli (E. coli), enterococcal bacteria, total coliform bacteria, and nitrates/nitrites. These parameters are the ones that are most likely to vary over time, and it is recommended that you include them in the regular monitoring done on the quality of well water.

Microbiological indicators of water quality

The majority of pathogenic micro-organisms (potentially disease-causing viruses, bacteria or protozoa) that are likely to be found in water come from human and animal excrements. As it is technically impossible to analyze all pathogens, we use microbiological indicators that in themselves are harmless: E. coli bacteria, enterococcal bacteria, and total coliform bacteria.

E. coli bacteria are very abundant in the bowel flora of humans and animals, and this is the only species that is strictly fecal in origin. E. coli bacteria are considered to be the best indicator of fecal contamination. Their presence in water means that it has been contaminated by pollution of fecal origin and that it may contain pathogenic microorganisms.

Gastroenteritis is the illness most commonly associated with drinking water contaminated with fecal matter. While this disease is often minor, it may occasionally have very serious consequences on a person’s health. Other rarer diseases such as hepatitis or meningitis may also result from the ingestion of contaminated water. This risk concerns not only the members of a family who drink well water, but also all their visitors.

Enterococcal bacteria are less abundant in the bowel flora of humans and animals than E. coli bacteria, and some species are not of fecal origin. The detection of enterococcal bacteria in well water may indicate fecal contamination or infiltration of surface water. However, it is best to play it safe and consider the presence of enterococcal bacteria as an indicator of fecal contamination.

Total coliforms form a heterogeneous group of bacteria of fecal and environmental origin. Indeed, most of the species may be naturally occurring in the soil and in vegetation. Their presence in water does not generally indicate fecal contamination or a health risk, but rather a deterioration of the bacterial quality of the water. This deterioration may be attributed among other things to the infiltration of surface water in the well, or the gradual growth of a layer of bacteria on the walls, called a biofilm. The analysis of total coliforms makes it possible to obtain information on the potential vulnerability of a well to surface pollution.

Presence of E. coli or enterococcal bacteria in my water

Drinking water must be free of any trace of E. coli or enterococcal bacteria. When either type of bacteria is detected, it is essential that you boil the water for at least one minute before consuming it, obtain drinking water from a public water system, or buy bottled water. You must also use boiled water to make ice cubes, prepare drinks and food for babies, wash food that will be eaten raw, and brush your teeth. You can continue using the well water to shower or bathe (being careful to avoid swallowing it), but you should give children and babies a sponge bath. These recommendations must be followed until subsequent tests show that the water complies with applicable standards.

It is recommended that you determine the source of fecal contamination and take the appropriate remedial measures, if possible. A shock treatment to disinfect the well may be necessary, particularly if the contamination is caused by special circumstances (a thaw, abundant rain, etc.).

Take the following steps to disinfect a well:

Clean the well with a net , if possible, to remove foreign objects, deposits, animal or plant material, etc.
Pour bleach into the well according to the quantities mentioned in the following table entitled “Quantity of Bleach Required for Disinfecting a Well.”
Mix the bleach with the well water and, where possible, wash and brush the sides clean. You can also hook up a hose to the nearest tap and rinse the sides of the well to ensure complete mixing of the chlorine and water in the well.
Turn all taps on. When you detect the smell of chlorine, stop the pump and turn the taps off.
Wait 24 hours before turning the water back on.
Purge the system by letting the water run for an extended period of time until the smell of chlorine disappears. Turn all the taps on to rinse the pipes thoroughly.
Test the water again one week and four weeks after disinfection to find out if the water complies with quality standards.

Presence of total coliforms in my water

The presence of total coliforms makes it even more important to conduct regular tests and take appropriate remedial measures to prevent any eventual fecal contamination. If new tests confirm the presence of total coliforms in concentrations exceeding the standards (above 10 ufc/100 ml), it is recommended that you give the well a shock treatment (disinfection).

Determining the source of contamination

It is important to identify the source of contamination and take appropriate remedial measures to improve the long-term quality of the water. There may be many local sources of contamination:

A well in poor condition (cover or sealant are not watertight, deteriorated materials, etc.)
Inadequate slope around the well (no mound around the well to keep away surface runoff)
Defective septic facilities
Unsanitary premises (e.g., manure spreading or other activities generating fecal matter nearby

In such cases, work should be undertaken to correct the situation or bring it to the attention of the person responsible for the source of contamination. Anyone confronted with a contamination problem can get in touch with the appropriate municipal official, who will help find a solution. Additional water tests should be done to check if the measures taken were effective.

The quality of my well water during a flood

Owners of private wells must take special precautions during floods, as such events can pose serious risks for the quality of groundwater, which can be contaminated by river water or septic facilities nearby. To prevent risk of illnesses related to drinking contaminated water, MDDEP recommends the following measures:

During the flood: water from any well in the flooded area should be considered to be unfit for drinking. In such cases, you should obtain drinking water from another source (e.g., a public water system or bottled water) or boil any water intended for drinking or preparing raw food for one minute.
After the flood: after the floodwaters have completely subsided, owners should first check the well equipment, especially the electrical circuits. They should then wait a minimum of ten days before disinfecting the well according to the procedure described in a previous section and ensure that the results of both series of recommended water tests are in compliance before drinking the water again.

Quantity of bleach required for disinfect a well

It is recommended that you use 50 mg/l of free chlorine to disinfect an existing well (use 5% fragrance free bleach available in stores). To disinfect a new well, multiply the amount of bleach by five as the recommended concentration is 250 mg/l of free chlorine.

The tables below will help you determine the quantity to use according to the diameter and depth of your well.

Quantity required for a surface well

Surface wells are generally made of superimposed concrete pipes over 600 millimeters in diameter. They are rarely more than 9 meters deep.


Surface Well	Well depth (metres)
Well diameter (millimetres)	1	1.5	2	2.5	3	3.5	4
Millilitres of bleach
914	700 ml	1 000 ml	1 300 ml	1 600 ml	2 000 ml	2 300 ml	2 600 ml
1 067	900 ml	1 400 ml	1 800 ml	2 200 ml	2 700 ml	3 100 ml	3 600 ml
1 219	1 200 ml	1 800 ml	2 300 ml	2 900 ml	3 500 ml	4 000 ml	4 700 ml
1 372	1 500 ml	2 200 ml	3 000 ml	3 700 ml	4 400 ml	5 200 ml	5 900 ml
1 524	1 800 ml	2 700 ml	3 700 ml	4 600 ml	5 500 ml	6 400 ml	7 300 ml
1 676	2 200 ml	3 300 ml	4 400 ml	5 500 ml	6 600 ml	7 700 ml	8 800 ml

Quantity required for a cased or artesian well

Cased wells are drilled when the groundwater is deep or the surface is rocky. They are generally made of steel pipe less than 80 millimeters in diameter and over 6 meters long.

Cased or Artesian Well	Well depth (metres)
Well diameter (millimetres)	15	30	45	60
Millilitres of bleach
50	30 ml	60 ml	90 ml	120 ml
65	50 ml	100 ml	150 ml	190 ml
76	60 ml	140 ml	200 ml	270 ml
89	90 ml	190 ml	280 ml	400 ml
102	120 ml	250 ml	370 ml	500 ml
127	190 ml	380 ml	570 ml	800 ml
152	270 ml	540 ml	820 ml	1 100 ml

Calculation tool for disinfecting wells

Nitrates/nitrites

The main sources of nitrates/nitrites are agricultural fertilizers, manure, household wastewater, and the decomposition of plant and animal organisms. Because they find their way into surface and groundwater through rain and melting snow, infiltration is greatest in the spring and fall.

Presence of nitrates/nitrites in my water

Over 5 mg/l

A nitrate/nitrite concentration over 5 mg/l in a well generally indicates the influence of agricultural activities and calls for testing of this parameter at least twice a year, as concentrations can increase over time.

Over 10 mg/l

If the concentration of nitrates/nitrites detected in the water exceeds the standard set out in the Regulation respecting the quality of drinking water, namely 10 mg/l, this water must not be used to prepare food for infants or pregnant women. Wherever possible, the general public must also avoid regularly consuming water whose nitrate/nitrite concentration exceeds the set standard. For more information on the applicable recommendations, those concerned are invited to contact their regional public health office.

Identifying the source of contamination

It is important to identify the source of contamination and carry out the necessary work. The contamination may be caused by the spreading of manure or chemical fertilizers near the well, or by nearby septic facilities. You can contact a representative of the regional office of Ministère du Développement durable, de l’Environnement et des Parcs in your area to help you find an appropriate solution.

My water still does not meet the quality standards

If all the aforementioned steps do not resolve the problem, it is still possible to obtain good quality water by installing one or more treatment devices specially designed to eliminate the problems revealed by the test results. Régie du bâtiment du Québec determines the requirements as to the type of treatment devices that can be installed in homes. To select the appropriate system, you can contact a firm specializing in water treatment. Products certified according to NSF/ANSI standards are recognized as effective in meeting the quality criteria. It is essential that such treatment systems be installed by a qualified professional, and used and maintained according the manufacturer’s recommendations.

Having my water tested…

To have your well water tested, it is recommended that you call on one of the laboratories accredited by Ministère du Développement durable, de l’Environnement et des Parcs. The full list of accredited laboratories is updated regularly on the MDDEP website. The laboratory immediately notifies the owner if the water does not meet the established standards.

In addition to the aforementioned tests, an analysis of arsenic, barium, and fluorides―substances that may be naturally occurring in groundwater and that pose a health risk―is also required for new wells. While this regulatory provision does not apply to existing wells, MDDEP considers that owners of such wells should have these tests done at least once.

Analysis of other parameters (hydrocarbons, solvents, pesticides, etc.) may also be in order if pollution-generating activities are suspected in your area.

It is generally recommended that you contact the public health office in your area whenever a chemical standard is exceeded for information on whether the water is fit to drink. The addresses and telephone numbers of the regional health and social services boards may be found at the following website address: http://www.msss.gouv.qc.ca/reseau/regies.html.

Samples must be collected properly to ensure the validity of the results. For more details, you can consult the document entitled Methods for taking and preserving samples for the application of the Regulation respecting the quality of drinking water, available on the MMDEP website. You will also find on this site the document entitled Le puits, published by the Ministère du Développement durable, de l’Environnement et des Parcs and intended specifically for owners of private wells. This document contains, among other things, important information on safe well construction, water quality monitoring, and appropriate treatment systems.

For more information

Contact MDDEP’s information center or its regional office in your area.