Well water: what to know before you filter
In short
If you are supplied by a private well, nobody monitors your water for you: testing is entirely your responsibility. The Quebec government recommends bacteriological testing twice a year, in spring and autumn, and physico-chemical testing once a year. Crucially, a reverse osmosis system is not a recognised disinfection barrier against bacteria. If your well shows coliforms, you need a UV steriliser, not just a membrane.
Updated
What nobody does on your behalf
A municipality distributing drinking water is required to test it regularly and publish the results. A private well falls under none of those controls: neither the city nor the ministry tests your water.
That is especially true in our service area. In Saint-Colomban, for instance, most homes are supplied by private wells. Each owner alone is responsible for knowing what they drink.
How often to test, and for what
The Ministry of the Environment recommends bacteriological testing twice a year — in spring and autumn, when runoff and snowmelt raise contamination risk. It covers E. coli, enterococci, total coliforms and nitrites-nitrates.
Physico-chemical testing, once a year, covers pH, hardness, calcium, magnesium, iron, manganese, metals and turbidity. A full analysis is recommended every three to five years.
Arsenic deserves at least one test over the life of the well: it occurs naturally in certain Quebec rock formations, it is odourless and tasteless, and nothing signals it.
Manganese, the most recent standard
Since 21 June 2024, Quebec's Drinking Water Quality Regulation sets a manganese standard of 0.12 mg/L, or 120 micrograms per litre.
The standard primarily targets infant health: at high concentrations manganese can harm children's neurological development, and babies fed formula made with tap water are particularly sensitive.
Manganese is common in Quebec groundwater. It sometimes announces itself through brownish water or laundry stains, but it can also exceed the standard with nothing visible at all. Only a test will tell.
What reverse osmosis handles on well water
A reverse osmosis membrane is highly effective on dissolved contaminants: arsenic, manganese, nitrates, fluoride, uranium, heavy metals. On mineral-heavy well water it is the most complete point-of-use technology available.
Pre-treatment is often required. Water heavy in iron, very hard or turbid fouls the membrane quickly; a sediment filter or a softener then goes upstream. That is one reason a well installation sits higher in our price range.
The safety point that has to be said
- Reverse osmosis is not certified as a biological disinfectant. It physically retains a large share of bacteria and viruses, but it is not a recognised disinfection barrier, and recontamination can occur downstream of the membrane, in the tank or the tubing.
- If your test shows coliforms or E. coli, the answer is a UV steriliser certified to NSF/ANSI 55 Class A, designed precisely for microbiologically unsafe water. We install that option, and we will not let you leave with a membrane alone in that case.
- UV only works on clear water. If the water is turbid, microorganisms shelter behind particles and survive the passage under the lamp. Pre-treatment is therefore not optional.
Frequently asked questions
Twice a year for bacteriological testing, in spring and autumn, per the Ministry of the Environment's recommendation. Once a year for physico-chemical testing, and a full analysis every three to five years.