Richmond Hill, ON repair guide
Basement Flooding in Richmond Hill: Groundwater From the Oak Ridges Moraine, Sewers From York Region
The Oak Ridges Moraine is a ridge of sand and gravel that stores rain and releases it slowly as springs, and Richmond Hill is built on top of it. Lake Wilcox, Bond Lake and the kettle lakes of Oak Ridges are the visible part; the invisible part is a water table that sits close to basement floors across the north of the city and keeps sump pumps running in August. South of Major Mackenzie the problems are more ordinary: 1970s and 80s subdivisions with silted weeping tile and sewers that surcharge in summer storms. This guide sorts groundwater from sewer backup, explains what each fix does, and says who owns which pipe.
By Michael, founder, fixmystuff.ca · Reviewed and updated 2026-09-11 · About 7–10 minutes
Groundwater on the moraine, sewer backup below it
North of Major Mackenzie, in Oak Ridges, Jefferson and around the lakes, groundwater is the default. It arrives clear at the wall-floor joint and through cracks, it does not wait for a storm, and a house there needs a sump system that works every month of the year, with a battery backup for the outages. In the older subdivisions to the south, clay weeping tile has silted up after forty years and groundwater appears after long rains and in the thaw; sewer backup arrives at the floor drain during a summer storm and smells like sewage.
Photograph where the water first appeared and when. Constant clear water is the moraine; storm-driven sewage is the sewer; a wet corner after rain is drainage or grading.
| What you see | Likely cause | Who fixes it |
|---|---|---|
| Clear water year-round, pump running in August | Moraine groundwater | Plumber: sump system with backup; drainage |
| Sewage from the floor drain in a storm | Sewer surcharge | Plumber: backwater valve |
| Clear water after long rain, older house | Silted weeping tile | Waterproofer or plumber: drainage, sump |
| Water over a window well | Surface water, grading | Grading, well covers, downspout extensions |
What the fixes do, and what the City has offered
A sump pump with a pit collects groundwater from the foundation drain and pumps it outside; on the moraine it may run thousands of hours a year, so buy a quality pump, a second pump or a battery backup, and a high-water alarm. A backwater valve is a one-way flap on the sanitary lateral that closes when the sewer surcharges so sewage cannot flow back into the house; while it is closed nothing in the house drains. Disconnecting the foundation drain from the sanitary sewer, where it is connected, takes groundwater out of the overloaded system.
Richmond Hill has offered subsidy programs for backwater valves and related flood protection at eligible homes, with conditions that the work be done by a licensed plumber under a City permit. The programs change; read the City’s current page before signing a quote.
- City’s current subsidy program checked for eligibility
- Licensed plumber and City plumbing permit number
- Camera inspection recording and locate
- Sump pump run hours, backup and alarm
- Grading and downspouts checked around the foundation
Who owns which pipe
In Richmond Hill the owner is responsible for the sewer lateral on private property up to the property line, and the City for the section from the property line to the main; York Region operates the trunk sewers and treatment and the water supply behind the City system. A camera inspection with a locate tells you which side a break or blockage is on. Keep the recording; an insurer will want it for a sewer backup claim, and sewer backup and overland water are usually separate add-ons on an Ontario home policy.
Properties on the moraine that were on private wells until York Region extended services may still have an abandoned well on the lot; a plumber excavating for drainage should know where it is.
Living with the moraine
A house on the moraine will always have water around it; the goal is to manage it, not to stop it. Grade the lot so surface water runs away, extend downspouts, keep the sump pit clean, test the pump and the backup every spring and fall, and consider a second discharge line in case the first freezes. The Toronto and Region Conservation Authority regulates work near the lakes and streams, and the Oak Ridges Moraine Conservation Plan limits what can be built and where; ask before excavating near a watercourse.
Questions to ask before booking
- Will you camera the lateral and give me the recording and locate?
- Does the City’s current program cover this work, and will you pull the City permit?
- Is the sump system sized for a pump that runs year-round, with a backup and an alarm?
- Is the foundation drain connected to the sanitary sewer, and should it be disconnected?
- What is the warranty on the devices and the workmanship?
Frequently asked questions
Why does my Richmond Hill sump pump run in dry weather?
The Oak Ridges Moraine stores water and releases it slowly, so the water table under Oak Ridges and the north of the city stays high year-round. The pump is doing its job; make sure it has a backup and an alarm.
Does the City of Richmond Hill help pay for a backwater valve?
The City has offered subsidy programs for backwater valves and related protection at eligible homes, with conditions on the plumber and the permit. Check the City’s current program page before signing a quote.
Who repairs a broken sewer pipe under my Richmond Hill property?
You do, for the section on private property up to the property line; the City handles the section to the main, and York Region runs the trunk sewers behind that. A camera locate shows which side the fault is on.
Can I excavate near Lake Wilcox for drainage?
Work near the lakes and streams is regulated by the Toronto and Region Conservation Authority and the Oak Ridges Moraine Conservation Plan. Ask before digging.
Nearby communities
York Region plumbers cover Richmond Hill, Aurora, Newmarket and Markham, and the moraine runs under Aurora and Newmarket as well. Flood-protection subsidies are municipal; ask what applies at your address.
Browsing more broadly? Start from the Richmond Hill repair hub for every local guide in one place.
Sources and further reading
- City of Richmond Hill: basement floodingCurrent subsidy programs, backwater valves and who owns which pipe.
- York Region: water and wastewaterHow the regional and city systems divide responsibility.
- Toronto and Region Conservation AuthorityPermits for work near lakes and watercourses on the moraine.
- Insurance Bureau of Canada: water damageSewer backup and overland water coverage.
Prices, programs, and acceptance rules can change. Check each source and obtain a written local quote before deciding.