Carbon monoxide alarm went off near my Calgary water heater, what now?

Get everyone out of the house right now, including pets, and call emergency services from outside. Do not stop to look for the leak, do not turn anything on or off, do not go back inside until emergency services tell you it is safe. Carbon monoxide is colourless and odourless, and exposure can incapacitate quickly.

Once the building is cleared

When emergency responders have checked the space and cleared you to re-enter, do not simply reset the alarm and carry on. A CO alarm near a water heater is a serious signal that the appliance may be producing or venting combustion gases into the living space rather than exhausting them safely outdoors.

Do not operate the water heater again until a certified gasfitter has inspected it. In Alberta, gasfitting is a compulsory certification trade under the Skilled Trades and Apprenticeship Education Act. The person who inspects and works on the appliance must be a certified journeyperson gasfitter or a registered apprentice working under one. Ask to see the certificate before work begins.

Common things a gasfitter checks in this situation: the flue or vent pipe for blockages, disconnection, corrosion or back-drafting; the burner and heat exchanger for cracks or incomplete combustion; and the combustion air supply to the appliance. The gasfitter designs any repair to CSA B149.1, the natural gas and propane installation code in force in Alberta since March 1, 2026, and the City of Calgary's inspector verifies the work.

Permits: any repair that alters the gas piping or venting on a water heater requires a gas permit from the City of Calgary. In Calgary, a homeowner cannot obtain a gas permit unless they are a certified journeyman gasfitter themselves; gas work here is for a certified gasfitter pulling the permit. A like-for-like appliance swap with no change to the gas line upstream of the shut-off valve and no change to the venting does not require a permit, but if the gasfitter finds the venting needs to change, a permit is required before that work starts.

Before the gasfitter begins, ask for a WCB-Alberta clearance letter confirming their account is in good standing, and check that any contractor taking a deposit before completing the work holds an Alberta prepaid contracting licence through Service Alberta. Get the scope, price and warranty terms in writing before signing anything.

If the water heater needs replacing, a standard 50-gallon gas tank supplied and installed typically runs $1,500 to $3,500 in Calgary; a tankless unit installed runs $2,200 to $5,000, plus $400 to $1,500 if the gas line needs upgrading. Those are typical Calgary figures for 2025-2026 and shift with equipment choice, access and what the gasfitter finds with the venting.

When you compare quotes, ask each gasfitter to spell out exactly what venting work is included, because that is where the price difference between two otherwise similar quotes is most likely to be hiding.