Basement Flooding in London, Ontario: Clay Soils, Sump Pumps and the City’s Grant Program

Groundwater, sewer backup or surface water

Groundwater on London clay rises after every long rain and during the spring thaw, and it comes in at the cove joint where wall meets floor, through cracks, and up through the floor of older basements with no drainage. Sewer backup arrives at the floor drain, a basement toilet or the laundry standpipe during or just after a heavy storm, and it smells like sewage; the older neighbourhoods on combined sewers are the most exposed. Surface water comes over window wells and under doors where grading slopes toward the house, and it is often the cheapest to fix.

Photograph where the water first appeared and when. That answer decides whether you need a plumber for a backwater valve, a waterproofer for drainage, a landscaper for grading, or a call to the City about the connection.

The City’s Basement Flooding Grant Program

The City of London’s Basement Flooding Grant Program contributes toward the cost of protective work at eligible homes: installing a backwater valve on the sanitary lateral, installing a sump pump and pit, and disconnecting the weeping tile from the sanitary sewer so groundwater no longer loads the City system. The work must be done by a licensed plumber under a City plumbing permit and inspected, and the grant is claimed after completion. Read the current program page before signing a quote; the eligible amounts and rules change.

A backwater valve closes when the sewer surcharges so sewage cannot flow back into the house; while it is closed, nothing in the house drains, which is why plumbers say not to run water during a storm. A sump pump moves groundwater from the foundation drain outside; on London clay a battery backup is worth its cost, because the storms that flood basements also cut power.

• Eligibility confirmed on the City’s program page
• Licensed plumber and City plumbing permit number
• Camera inspection recording and locate
• Itemized invoice for valve, pump and labour
• Grant claim submitted after completion

Who owns which pipe

In London the owner is responsible for the sewer lateral on private property up to the property line, and the City for the section in the road allowance to the main. A camera inspection with a locate tells you which side a break or root blockage is on. If it is the City’s side, call the City; if it is yours, the repair is yours. Keep the recording, because an insurer will want it for a sewer backup claim.

Sewer backup and overland water are usually separate add-ons on an Ontario home policy, and insurers ask whether a backwater valve is installed. Check both before the next storm.

Clay, older houses and cheap fixes first

Houses in Old East, Old South and Wortley from the 1900s to 1930s often have no weeping tile at all and brick or block foundations that clay-held water passes through. Waterproofing there is excavation, a membrane and new drainage, sometimes with a mason. Post-war houses usually have clay weeping tile that has silted up, which a sump system can serve. Either way, extend downspouts well away from the foundation and correct grading before spending on anything underground; on clay, the water you keep away from the wall is water that never gets in.