Burlington basement flooding reached mechanical rooms across the city in August 2014 and again in July 2024, and protecting your furnace comes down to two things: height before the storm and replacement of parts after it. A gas valve or control that has been under water is replaced, never dried out and reused. Before the next storm, the measures that work are a furnace and water heater raised on stands, condensate pumps and controls moved up the wall, and sealed-combustion equipment. If your furnace has been wet, leave it off and have it inspected before it runs again.
Which Burlington Basements Put the Mechanical Room at Risk
Risk follows the way water gets in, and Burlington has two ways. Overland flooding comes through window wells, walkout doors and reverse-slope driveways when a storm overwhelms the creeks that run from the escarpment down to Lake Ontario. Sewer backup comes up through the floor drain when the sanitary system is surcharged with stormwater.
- Houses near a creek or at the low point of a street, where overland water collects.
- Homes from the mid-1950s to the late 1970s, the era Halton Region's household drainage surveys focus on, where downspouts or weeping tiles may still be connected to the sanitary sewer.
- Basements with a below-grade entrance, a reverse-slope driveway or deep window wells.
- Sump pits with a single pump and no battery backup, since storms and power failures arrive together.
- Finished basements where the furnace sits in a closet at the lowest point of the slab.
The mechanical room is usually the first place water appears. Furnaces and water heaters are placed beside the floor drain on purpose, so their condensate and relief lines have somewhere to go, and the floor is sloped toward that drain. When the drain backs up, the equipment is standing in the deepest water in the house.
What Flood Water Does to a Furnace and Water Heater
Water ruins the parts that keep a gas appliance safe, and it reaches them quickly because the most sensitive parts sit lowest. In an upflow furnace the blower compartment is at the bottom of the cabinet, with the burner and gas valve just above it. Ten centimetres of water can be enough to reach the motor.
- Gas valve: its internal regulator, diaphragm and vent corrode after immersion. A valve that sticks open or fails to close fully is a fire and carbon monoxide hazard, and it cannot be judged from the outside.
- Blower motor and its electronic module: bearings wash out and windings short, sometimes weeks later.
- Control board, igniter, flame sensor, pressure switch and limit switches: silt and corrosion on contacts cause intermittent faults that are hard to trace.
- Burners and heat exchanger: silt blocks burner ports and rust begins on bare steel.
- Cabinet insulation: the liner holds contaminated water against the metal and sits in the air stream, so it has to come out.
- Water heater: the gas control and burner chamber are at the base of the tank, the air-intake screen underneath clogs with silt, and the insulation between tank and jacket never dries.
After Submersion: Replace the Gas Valve and Controls, Do Not Dry Them Out
Any gas control or electrical component that has been under water is replaced. That is the position of the equipment manufacturers and it is how a licensed gas technician has to treat the appliance. A furnace that starts after being dried with a fan has not been proven safe.
- Stay out of standing water until the power to the basement is off.
- If you can reach it safely, close the gas shutoff at the appliance. Do not relight a pilot or press a reset button.
- Photograph the water line on the furnace and water heater cabinets for the insurer.
- Have a TSSA-licensed technician inspect before the equipment runs. An appliance found unsafe is tagged and shut off until it is repaired or replaced.
- Ask for the findings in writing, since insurers normally want a technician's report.
The repair-or-replace decision follows the water line. Water that only wet the floor under a furnace on blocks calls for an inspection and often nothing more. Water that reached the blower, burner or gas valve means those parts at minimum, and the bill adds up: a gas valve is $500–$1,000, a control board $500–$1,200 and a blower motor $500–$1,500.
Free quotes, written pricing.
Our rule: replace the whole furnace when the water was sewage, when the cabinet was submerged past the burner, or when the furnace is over 12 years old and needs more than one of those parts. A high-efficiency furnace installs for $4,500–$7,500 and a tank water heater for $1,200–$2,500. Our flooded furnace replacement page covers the insurance paperwork, and the first-hour steps are in our answer on what to do if your furnace was flooded.
Protection Measures That Work Before the Next Storm
Lift what you can and seal what you cannot lift. Most of these are far cheaper during a planned replacement than as a separate project, so raise them when the furnace or water heater is being changed anyway.
- Raise the furnace on a stand or platform: even 20 to 30 cm clears a shallow backup. Ceiling height, the supply plenum and the vent pipe set the limit, and where an upright stack will not fit, some furnaces can be installed horizontally and hung from the joists.
- Raise the water heater: a tank on a rated stand, or a wall-hung tankless unit mounted well above the floor, takes the gas control out of reach of shallow water.
- Relocate the condensate pump and controls: mount the pump on the wall with its safety switch wired to stop the furnace if it fails, and lift low-voltage splices, the humidifier valve and the furnace's receptacle above the expected water line.
- Choose sealed-combustion equipment: a two-pipe furnace or direct-vent water heater draws combustion air from outdoors through a sealed pipe. It is not waterproof, but it has no open draft hood or floor-level air opening for water and debris to enter.
- Add a water alarm at the floor drain: an inexpensive sensor gives you time to shut the equipment off.
- Move the furnace out of the basement: for a house that has flooded more than once, relocation to a main-floor closet or a raised utility room is worth pricing.
The outdoor unit needs the same thinking. A condenser or heat pump in a low side yard or beside a window well can be set on a taller stand, which also keeps it clear of snow.
Halton Region's Subsidy and the City's Grant for the Plumbing Side
Keeping water out of the basement is plumbing work, and there is public money for it. Halton Region's Basement Flooding Prevention Subsidy Program covers backwater valve installation, downspout disconnection, exterior storm drain disconnection, weeping tile disconnection with a sump pump, and wastewater lateral lining and repair. The Region's homeowner guide sets out the amounts and eligibility, and Halton answers questions at 311.
The City of Burlington adds a plumbing permit fee grant for backwater valves, sump pumps and sanitary line repairs. A licensed plumber does that work. We handle the gas and HVAC side: raising, replacing or relocating the equipment once you know how high the water is likely to reach.
Verdict: What to Do Now
Spend on height first. A stand under the furnace and water heater and a relocated condensate pump protect against the shallow water a failed sump pump or a backed-up floor drain leaves behind, at a fraction of what a replacement costs.
- Furnace or water heater has been wet: leave it off, call for an inspection, and expect the gas valve and controls to be replaced at minimum.
- Dry so far, equipment under 10 years old: wall-mount the condensate pump, add a water alarm and get the sump and backwater valve looked at by a plumber.
- Dry so far, equipment due for replacement: put the new units on stands, choose sealed combustion and consider a wall-hung tankless heater.
- Flooded more than once: price relocating the furnace out of the basement.
Insurers ask about mechanical equipment after a water claim, and our guide to furnace inspections for home insurance explains what they look for. For a furnace that will not run after water in the basement, see our furnace repair service and our Burlington service area page. Our emergency line at (647) 801-1252 is answered 24/7, or you can send us the details and photos and we will tell you what the inspection involves.
Frequently asked questions
Can a furnace be used after it has been in flood water?
Not until a licensed gas technician has inspected it and replaced what was submerged. The gas valve, controls, wiring and usually the blower motor are replaced if the water reached them, and wet cabinet insulation comes out. If sewage was involved or the furnace is older, full replacement is normally the sounder and cheaper route.
How high should a furnace be raised off the basement floor?
As high as the ceiling, the ductwork and the vent pipe allow, with 20 to 30 cm a realistic target where headroom is tight. That clears a typical floor-drain backup or failed sump pump. It will not protect against a deep overland flood, which is why a backwater valve, a sump pump with battery backup and lot grading matter as well.
Does home insurance cover a furnace damaged by a basement flood?
It depends on the policy. Sewer backup and overland water are usually separate endorsements, not part of basic coverage, and each has its own limit and deductible. Read your policy or call your broker before a storm, not after. When there is a claim, the insurer generally asks for a technician's written assessment of the equipment.
Is a tankless water heater safer from flooding than a tank?
It is better placed. A tankless heater hangs on the wall with its burner and controls about chest height, well above a shallow flood, while a tank's gas control sits near the floor. Water deep enough to reach a wall-hung unit will still damage it. The condensate line and its pump, if it has one, should be mounted high too.