Everything you need to know about your septic tank in Quebec

Updated April 13, 2023

Homes and facilities in rural and remote areas are not connected to municipal sewer lines. Have you ever wondered how wastewater is dealt with in these areas?

It all happens with the installation and maintenance of a septic tank—effectively an onsite wastewater treatment system. If your home in Quebec has a septic tank or you’re thinking of having one installed, read on! You’ll find out how they work, the different options available, pricing, maintenance and how they impact your home insurance.

Concrete septic tank

What is a septic tank?

A septic tank is a wastewater treatment system located on your property. This system includes a tank, pipes, and a septic drain field. Septic tanks come in different sizes and materials, such as concrete, polyethylene, fiberglass and steel. Household septic tanks generally have a capacity of between 3,000 and 7,500 litres and eliminate at least 60% of solid waste.

How do septic tanks work?

The wastewater from your toilets, sinks and other drains flow through pipes into the septic tank.

The tank is designed to retain wastewater long enough so the solid waste can sink to the bottom. This is referred to as “sludge.” Meanwhile, oil and grease rise to the surface to form a layer of scum that helps prevent leaks and allows enzymes to break down the organic waste into smaller molecules which are consumed by anaerobic bacteria.

Fun fact

The word septic originates from the Ancient Greek sēptikós, which roughly translates to “characterized by putridity.” That’s another way of saying the septic tank is a tank full of bacteria breaking down matter.

The septic process allows the waste to liquify and flow through an evacuation pipe to the septic drain field or leach field/drain. From there, it is spread through perforated pipes surrounded by crushed gravel. The water infiltrates and percolates in the ground where microorganisms eliminate what remains of any toxic substances in the wastewater. This treated water slowly makes its way back into the groundwater to complete the water cycle.

An example of a septic system with the covering ground removed

Types of septic tanks

  • Concrete septic tanks are the most popular kind of system because of their lower cost and greater durability. They usually come prefabricated for easy installation. Despite their durability, concrete septic tanks can crack and corrode. The bacteria in septic tanks produce hydrogen sulfide, which Thiobacillus bacteria in turn convert into hydrosulfuric acid. Needless to say, acid can corrode the concrete.
  • Polyethylene septic tanks are lighter than concrete systems and resist corrosion. However, they are thinner than concrete septic tanks, which makes them vulnerable to structural damage. Although they are easier to transport because of their lighter weight, they can be easily damaged if they are not handled with care. They can also crack under pressure.
  • Fiberglass septic tanks are lightweight, making them easy to transport and install. While they are more durable than polyethylene tanks, they are the most expensive option due to the higher operating and maintenance costs.


The price for installing a septic tank varies depending on the material, the size of the home and the quality of the soil, among other factors. A standard system will cost anywhere from $3,000 to $12,500. If your soil isn’t very penetrable or the water table is too high, you will need an advanced system, which can cost between $15,000 and $30,000.


Before designing and installing a new septic tank, a qualified engineer must assess your property. The engineer will examine the soil and determine the size of the system based on the number of bedrooms in your home.

The company you hire for the installation must adhere to the standards set by the ministère de l’Environnement et de la Lutte contre les changements climatiques (MELCC). In Quebec, homeowners do not have the right to build their own septic system, however they may replace or repair an existing system by obtaining a permit from their municipality.

When to empty septic tanks

In Quebec, septic tank maintenance falls under provincial jurisdiction. Regulations in Quebec mandate that septic tanks be drained every two years, with the exception of secondary residences, whose septic tanks should be drained every four years.

This task must be performed by qualified professionals because septic tanks produce toxic gases containing pathogenic bacteria.

Home insurance considerations

Many home insurance providers offer coverage for water backups (which typically includes septic systems), though you’ll often need to add the coverage specifically and pay extra.

Square One includes water and sewer backup coverage on every policy we sell.

However, if the water backup is caused by heavy rainfall or another weather occurrence, your insurer may treat it as a flooding event. That would mean your policy’s flood coverage applies—including any higher flood deductibles or even outright exclusion. Cities and regions with a high flood risk may be excluded.

Some home insurance providers may also offer a discount if your home has a backwater valve installed on the wastewater line. While these valves are commonly associated with homes connected to municipal systems, they can help prevent sewer backup from septic tank systems, too.

Check your policy wordings or speak to your provider if you’re unsure how your home insurance policy treats septic tanks and water backups.

Commonly asked questions

How do I know if I have a septic tank?

If your home is located outside the city or in a rural or remote area, where a municipal sewer system would be too expensive to build and maintain, you most likely will have a septic tank.

Another way to tell if you have a septic tank is to look for cylindrical lids or an unusual lump of earth on your property. These are typically indicators that your property has a septic system.

The simplest way to tell is to see if sewer fees are listed on your municipal tax account. If they are, that means you are connected to the municipal sewer network.

How do I know what size of septic tank to choose?

The size of your septic tank depends on the number of bedrooms in your home.

A five-bedroom house would require a septic tank with a capacity of approximately 3,000 liters. The qualified professional you hire to assess your property will be able to tell you the exact size of tank you need based on the characteristics of your property.

If I have a septic tank, what products must I avoid flushing down the toilet?

Since a septic tank depends on enzymes and bacteria to break down organic waste, there are a number of industrial and household products that you must avoid flushing down the toilet. These include antibacterial products, cat litter, cigarette butts, cosmetic products, expired medicine, dental floss, latex condoms, paper towel, plastic, sanitary napkins, toilet paper and wet wipes, among others.

Besides harming the bacteria, these products can damage the septic tank and cost you a fortune in repairs. If you have guests or rent out your property, it is a good idea to post a notice to this effect in your bathrooms.

Want to learn more? Visit our Getting to Know Your Home resource centre for the complete rundown on all your home's systems and features. Or, get an online quote in under 5 minutes and find out how affordable personalized home insurance can be.


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