When researching how to protect your London, Ontario home from basement flooding, you will immediately run into two plumbing terms: Backwater Valves and Sump Pumps. (If you haven't yet, be sure to read our complete London Ontario Basement Flooding Grant Guide for the full breakdown of the city's rules).
While both are critical for flood prevention, they serve entirely different purposes, handle different types of water, and receive different levels of funding from the City of London’s Basement Flooding Grant Program.
If you want to maximize your municipal funding and fully protect your home, you need to understand how these two devices work together.
The Backwater Valve: Stopping City Sewage
A backwater valve is designed to manage the water inside your plumbing system (your wastewater).
During heavy rainfall in London, the municipal sanitary sewer mains under the street can become completely overwhelmed. When this happens, the flow of wastewater reverses. Instead of your sewage flowing out to the treatment plant, the city’s raw sewage begins pushing backward up your private drain connection and into your basement.
How it works: A backwater valve is installed directly into your main sewer line beneath your basement floor. It features a mechanical, one-way flap. Under normal conditions, the flap rests open, allowing your household wastewater to exit. However, if city sewage attempts to surge backward into your home, the flap automatically floats up and locks shut, physically blocking the raw sewage from entering.
What the Grant Covers: Because preventing sewer backups is a major priority, the City of London Basement Flooding Grant will cover 90% of the cost, up to a maximum of $1,800, to have a licensed plumber install an approved backwater valve.
The Sump Pump: Managing Groundwater
While a backwater valve handles sewage, a sump pump is designed to manage the groundwater outside of your home’s foundation.
Older homes in London (especially those built before 1985) often have their foundation drains (weeping tiles) connected directly to the sanitary sewer. The City desperately wants to break this connection so that clean groundwater stops overwhelming the sewage treatment plant.
How it works: A drainage contractor will disconnect your weeping tiles from the sanitary sewer and reroute them into a new "sump pit" dug into your basement floor. As groundwater accumulates around your foundation, it flows into this pit. The sump pump then actively pumps the water up and out of your house, safely discharging it onto your lawn or into a storm sewer.
What the Grant Covers: Disconnecting weeping tiles and installing a sump system is labor-intensive. Fortunately, the City of London grant covers 90% of the cost, up to a maximum of $4,000 for this specific work. (They also offer up to $1,400 for a battery backup system, provided it is installed alongside a brand-new pump).
📍 Consumer Advocate Warning: The City will NOT cover the cost of simply replacing an old, broken sump pump. The $4,000 grant is strictly for new weeping tile disconnections and initial sump pit installations.
Do You Need Both?
In many cases, yes. If your home has weeping tiles tied into the sanitary sewer, the City of London actually requires the installation of a backwater valve in conjunction with your weeping tile disconnection to qualify for the funding.
Together, these two devices form a complete shield: the sump pump keeps the groundwater out, and the backwater valve keeps the city's sewage out.
Ready to Get Started?
Securing up to $5,800 for these two devices requires strict municipal pre-approval and mandatory itemized quotes.
👉 Download our Free London Flood Grant Application Checklist Here