Most sewage that comes up a Collingwood floor drain has nothing to do with the storm sewer. It comes through your sewer lateral from the Town’s sanitary sewer, and the Town names two causes: a blockage in that lateral, which it calls the most common one, or a sanitary system that rain and meltwater have filled past its capacity. The fix, the bill and the chance of it happening again all depend on which one you had.
Two sets of pipes, and only one of them reaches your drain
Collingwood runs sewage and rain in separate pipes. Your toilets, sinks and floor drains feed a single sewer lateral that runs out under the lawn to the sanitary main in the street. Rain is meant to go somewhere else: onto the ground, or into the storm drains at the curb.
So “storm sewer backup” is really a sanitary sewer that a storm has overloaded. The Town’s wastewater services page describes how that happens. Stormwater and groundwater leak into the sanitary pipes through small cracks and through manhole lids. More arrives from private property, where downspouts or sump pumps are connected to the sewer instead of to the lawn. On an ordinary day the treatment plant runs at an average of 70% of its capacity. In an intense storm the Town says the flow into the plant can double or even triple.
That is the first cause, and it is the one the name suggests. It is not the one the Town sees most.
Cause one: a blockage in your own lateral
The Town’s page states it plainly: the most common cause of backed up drains or basement flooding in a home is a blockage in the sewer lateral. The usual suspects are tree roots, fat and grease, wipes and paper towels, and older pipe that has cracked or collapsed.
A blockage like that does not need a storm. It needs somebody upstairs to run the washing machine. But a storm makes a half-blocked lateral worse, because the sanitary main in the street is running full at the same moment, and the slow drain that has been tolerable for months finally gives up.
What points to this cause:
- It happened to your house and not to the neighbours.
- Drains had been slow before it happened, or the lowest toilet gurgled.
- The water came up while you were using water in the house, rain or no rain.
- There are mature trees between the house and the street.
Cause two: the sanitary main surcharging in a storm
When the main itself is overloaded, the water in it looks for a way out, and a basement fixture below street level is one. This is the version that arrives during a downpour or a fast spring melt, and it tends to hit several houses on the same low street at once.
What points to this cause:
- Neighbours had water too, on the same night.
- It came up during heavy rain or rapid snowmelt, not during a load of laundry.
- The Town posted a notice about a sanitary sewer overflow or bypass around the same time.
- Your drains work normally the rest of the year.
A bypass, where the plant diverts flow toward Georgian Bay, is the Town’s safety valve for exactly this. Its own explanation is that it happens to prevent sewage from backing up into residents’ basements.
Why it matters which one you had
Who fixes it. The lateral is yours. The Town’s page says property owners own and maintain it from inside the building to the connection with the Town sewer, and that the owner carries the cost even for the stretch under the road. Public Works repairs that stretch and bills 50% of time and materials, to a maximum of $6,000, under By-law 2020-015. The main is the Town’s.
Whether it happens again. A blocked lateral comes back until the roots or the broken section are dealt with. A surcharging main comes back in the next big storm, and the protection on your side is a backwater valve.
The valve question. In February 2013 Collingwood’s building department began requiring a backwater valve in every new home, according to the Canada in a Changing Climate case study on mandatory backwater valves. A house built before then may not have one. Fitting one is a plumbing job with a permit, not restoration work.
The claim. Most Ontario policies cover sewer backup only through an optional endorsement. The distinction between your lateral and the Town’s main rarely changes that, but the photographs of where the water came up do. Before you report anything, read whether I should claim water damage on insurance in Ontario.
What you can check this week
Walk outside and find where your downspouts end. If any disappear into the ground near the foundation, find out where that pipe goes. The Town asks that downspouts and sump pumps discharge onto the lawn or into the ground, and never into the basement floor drain.
Do the same with the sump pump. A discharge hose run into a laundry tub or floor drain puts groundwater straight into the sanitary sewer, which adds to the overload on your own street.
Find the sewer cleanout. The Town notes it must be located and accessible before anybody can clear a blockage, and a cleanout buried under a finished floor turns a short job into a long one.
Only flush toilet paper. That is the Town’s own message, and wipes marked “flushable” are on its list of things that block laterals.
If it has already happened
Stop using the plumbing until the cause is found, which is also the Town’s advice. Keep out of the room, and take pictures of the drain the water came up through before anything is moved. What to do after water damage covers the first hour in order.
Water that came up out of a sewer is Category 3 whichever cause put it there, so the porous materials it touched come out. That part does not change with the diagnosis. The containment, removal and drying are what we do for sewer backup cleanup in Collingwood. If the water came through the walls or the slab instead of up through a drain, that is basement flooding in Collingwood, and it is a different job. Either way, it falls under our water damage restoration in Collingwood coverage.