Why Mississauga Basements Flood

The entry in brief

Water reaches a Mississauga basement in one of four ways: up through the floor drain when sewers surcharge in a storm, through the foundation from saturated soil, from a failed sump pump, or from a burst or leaking pipe inside the house. Each has a different fix, and many homes are at risk from more than one.

What is going on

In heavy downpours, the sanitary and storm sewers can fill faster than they drain. In homes connected without a backwater valve, sewage can then push back up into the lowest drain. Older neighbourhoods are more exposed, especially where foundation drains or downspouts were once connected to the sewer system.

Groundwater is the second culprit. When soil around the foundation is soaked, water finds cracks, tie holes and the joint between the wall and the floor. Sump pits are designed to collect this water and pump it away, but they only work while the pump runs.

Inside the house, the usual suspects are washing machine hoses, water heater tanks, frozen pipes in winter, and older supply lines that finally give way.

In order

1. Walk around the outside. Check that downspouts are attached and their extensions carry water away. Look for low spots where water pools against the wall.
2. Find your floor drain and your sump pit, if you have one. Keep both clear and accessible.
3. Pour a few litres into the sump and check the pump kicks in, drains it and stops.
4. Find out whether you have a backwater valve. It hides under a round lid in the concrete, normally on the road-facing side.
5. Replace rubber washer hoses with braided ones, and check the base of your water heater for rust or damp.
6. Store papers and keepsakes up on shelving in lidded tubs, never on the slab.

Slips to avoid

• Assuming a dry basement last spring means a dry basement next spring. Pumps and valves wear out.
• Plugging a sump pump into an outlet that shares a circuit with a freezer or other heavy load.
• Covering a floor drain with carpet or boxes.
• Pumping water from the sump into the sanitary sewer through a laundry tub. That adds to the very surcharge that causes backups.
• Waiting until a storm warning to look for the main shut-off.

When the ledger says phone

Call us if water has come up through a floor drain, if your sump pump fails its test, if you want a backwater valve assessed or installed, or if you have water and cannot tell where it is coming from. In a live flood, our emergency plumber service is the line to use.

Seasonal timing helps too. Many floods follow a hard freeze and thaw, and our note on winterizing plumbing in Ontario is a good companion to this one. For help with the cost of protective devices, read our note on the Mississauga flood protection subsidy.