Septic tank pumping: how often and what to check

On the Island of Montréal, most houses are connected to the sewer. In the North and South Shore crowns of Greater Montréal, from the back roads of Mirabel to the wooded areas of Saint-Lazare, many properties still treat their wastewater with a septic system: a tank, then a treatment field (the leaching field). Quebec’s Regulation respecting waste water disposal systems for isolated dwellings (Q-2, r. 22) sets the rules; the municipality enforces them.

1. How often should the tank be pumped?

• Under section 13 of the regulation, a septic tank used all year must be pumped at least once every 2 years, and a tank used seasonally at least once every 4 years.
• When the municipality itself handles pumping, it may instead go by measuring the scum and sludge: the tank must then be emptied as soon as the scum layer reaches 12 cm or the sludge layer reaches 30 cm.
• Some municipalities organize pumping and bill it on the tax account; others ask the owner to hire a company and send proof. Ask before calling anyone.

2. Septic tanks in Saint-Lazare, Mirabel and Mascouche

In Saint-Lazare, the City (in French) reminds residents of the two-year pumping rule and asks them to send proof of pumping by December 31, in person at City Hall, by mail or by email to the planning department. Residents who think pumping is not needed can ask for a tank inspection by October 31: if the measured layers are below the limits, the obligation moves to the following year; if they are above, the tank must be pumped right away.

In Mirabel, the City’s water page (in French) reminds owners that they must make sure their septic system works properly at all times, because a failing or leaking system can contaminate groundwater; a map shows whether your lot is inside the protection area of a municipal well. Mirabel’s by-law 129 (in French) also forbids sending rainwater or water from building drains into a septic tank.

In Mascouche, the City’s septic systems page (in French) states that pumping must be done by a contractor accredited by the City (by-law R-1215) and that proof of pumping must reach the City before October 1 of the year it is due. To build a system, the City requires a permit, plans and specifications signed and sealed by an engineer or a professional technologist, then, as soon as the work is done, a certificate of compliance, which banks and notaries often ask for when a house is sold. The City also offers financial help to rebuild a non-compliant system. And according to its FAQ (in French), adding a bedroom in a house served by a septic system needs a permit.

To find a pumping or installation company nearby, see the pages for Mirabel, Saint-Lazare and Mascouche.

3. Signs of a problem

• Sewage smells near the tank, over the field or in the basement.
• Toilets and drains that empty slowly, gurgle or back up.
• Soggy ground, surface water or unusually green grass over the field.
• A well water test that finds bacteria, especially if the well is close to the system.

If you notice any of these, have the system inspected without delay: poorly treated wastewater can contaminate your well, your neighbours’ wells or a stream. See also our guide on well water.

4. Building, enlarging or replacing a system

• Under section 4 of the regulation, you need a municipal permit before building, renovating, altering, moving or enlarging a septic system, and also before adding a bedroom to an isolated dwelling: the tank’s minimum capacity depends on the number of bedrooms.
• The permit application relies on a characterization study of the site and natural ground, with a location plan, prepared by a qualified professional.
• The work must be done by a contractor whose RBQ licence includes subcategory 2.4 (on-site wastewater treatment systems). Check the licence before signing, and ask who files the permit application.

Renting out your cottage or house? Book the pumping before the season and keep the invoice: it is your proof. To compare offers, you can describe your septic project and get quotes.