Basement Flooding

Your home is your biggest investment, so it's important to keep it protected. Performing regular maintenance and planning ahead is the best way to protect your home against basement flooding. Doing a little bit of work upfront could save you time and money in the long run.

But you're not alone. The City is here to help, before, during and after a basement flooding.


 What to do if your basement is flooded


Report basement flooding to the City by calling 905.688.5600 and contact your insurance provider ASAP.

Determining the cause of basement flooding is not always easy. The City needs as much information as possible from affected residents, including:

  • Where is the water coming from?
  • When did it start?
  • How much water is there?
  • What is the clarity of the water?

Cleaning up a flooded basement

If the flooding is due to a burst water supply pipe in your home, and if you are safely able to do so, shut off the main incoming water valve. This could help minimize the damage.

Water from a burst supply line will be clean, and likely coming down through the house from an upper level.

If the flooding is due to a sewage backup (or you are not sure of the cause), do not flush the toilet, run a washing machine, dishwasher or any other feature with a drain since this is likely to increase the flooding.


Safety first:

  • Dress appropriately - wear overalls, gloves, protective eyeglasses, rubber boots and a mask.
  • Open windows to let fresh air in.
  • Turn off your home's power at the main breaker switches -- ONLY if you are certain you can safely do so. Don't take risks with electrical equipment. Consult an electrician if you're uncertain of potential electrical hazards.
  • Keep children and pets out of the area until cleanup has been completed.
  • Water could extinguish a pilot light on a gas appliance. If you detect gas, leave the house immediately and contact the gas company.
  • Discard all contaminated items that cannot be washed and disinfected.
  • Remove and discard drywall and insulation that has been contaminated with sewage or flood waters.
  • Wash all surfaces with hot water and liquid detergent, rinse and thoroughly dry and ventilate the area. Use a de-humidifier and fans if necessary.
  • Sanitize walls and floors.
  • Wash all clothes worn during the cleanup in hot water (check manufacturer's washing instructions) and detergent. These clothes should be washed separately from uncontaminated clothes and linens.
  • If in doubt, throw it out. Do not consume potentially contaminated food.

Other tips:

  • Eliminate excess water using old rags or towels. A wet/dry vacuum may also help with this.
  • Remove dry belongings as quickly as possible to prevent rot, mildew, mould and warping.
  • Keep an itemized list of items affected by the flood.
  • Organize what you can keep and what needs to be discarded. Don't let them mix together.

Preventing basement flooding

Residents can help protect themselves and their neighbours against basement flooding by following these tips.

  • Disconnect downspouts and sump pumps from the sanitary sewer system. During heavy rain, water discharged into the sanitary sewer from downspouts and sump pumps can overwhelm sewers, increasing the possibility of a sewer backup.

  • Install a backflow valve. Backflow valves are designed to stop the sanitary sewer from backing up into basements. The City's Flood Alleviation Program (FLAP) provides financial assistance to residents interested in installing a backflow valve or other flood alleviation measures.

  • Don't put kitchen waste, grease and oils down the sink as they can clog the sanitary sewer.

  • Seal cracks or openings in walls, floors, windows and foundations, and seal all window wells.
  • Repair/replace damaged weeping tile systems.
  • Clear eavestroughs and downspouts of leaves and other debris.
  • Ensure the grading around your home slopes away from the foundation wall. This will help water drain away from your home

  • A healthy garden with a mix of native plants and shrubs will help absorb rainwater and melted snow.
  • Clear debris from roadside catchbasins. Make sure it's safe to do so before you start.
  • Ensure ditches between properties are maintained and clear of obstructions.
  • Know the location of your water shut-off valves. 

Spring Thaw

Here are some things you can do in advance of the spring thaw to prevent against basement flooding:

  • Clear your eavestroughs and downspouts of snow and ice. Doing so will ensure water drains properly.
  • Make sure your downspouts are draining water away from your foundation's walls. Ideally, have the downspouts drain onto your lawn or garden.
  • Clear roadside and backyard catch basins (grates) to help water enter the storm sewer. Make sure it is safe to do so before you begin

Get to know your home's plumbing

It's important to know your home's plumbing and foundation drainage systems and how to maintain them.

  • Know the location and condition of your sewer lateral (the pipe that connects the plumbing in your home to the main line on the street).
  • Find out if you have a storm sewer lateral (pipe), and if so, the location and condition of it.
  • Find out if you have a backwater valve or sump pump, and if so, how to maintain them. Understand what is needed to keep a sump pump operational during power outages.
  • Find out if you have weeping tiles and if so, their condition and where they are connected.

Causes of basement flooding

Causes of basements flooding:

  • A crack or leak in your home's foundation, basement walls, or basement windows or door.
  • Poor lot grading or drainage.
  • Failure of the weeping tile system (foundation drains)
  • Failure of a sump pump to pump weeping tile water.
  • Overflowing eavestroughs.
  • Leaking or plugged downspouts.

Causes of sewer flooding:

  • A backup in the sanitary sewer lateral, which will usually result in flooding from the floor drain, toilets, sinks, showers and laundry fixtures located in the basement.
  • Blocked connection between your home and the main sewer in the street, a sewer main backup or when the sewer system becomes overwhelmed with stormwater.

Download our Flood Action Checklist for more tips to prevent flooding (PDF 634KB)

Copyright © 2014 The Corporation of the City of St. Catharines