Hot Water Tank Not Heating? Gas and Electric Fixes

Running out of hot water, or getting none at all, usually comes down to a few causes that depend on whether your tank is gas or electric. Before you start, check one thing that is especially common in Ontario: many homeowners rent their water heater rather than own it. Look for a monthly water heater rental charge on your gas bill or a separate bill from a rental company. If your tank is a rental, call the rental company first; repairs are usually included, and you should not modify a unit you don't own.

On electric tanks: a tripped breaker, a tripped high-temperature cut-off (the red reset button behind the upper access panel), or a failed heating element or thermostat. On gas tanks: an interrupted gas supply, a pilot light that has gone out on older models, a failed thermocouple, or on power-vented tanks (common in Ontario, with a fan on top and a plastic vent pipe to the outside) a tripped breaker, an unplugged fan, or a blocked vent. On both, a thick layer of sediment at the bottom of the tank reduces how much hot water you get, and a temperature dial turned too low gives lukewarm water.

A flashlight, a garden hose and bucket for flushing, a flat-head screwdriver, and a multimeter (CAD $20–$40) if you plan to test electric elements. Replacement elements cost about CAD $20–$40 and thermostats about CAD $20–$50 for most electric tanks.

1. Confirm whether the tank is rented. If it is, stop here and call the rental company.
2. Check the temperature setting. Health Canada recommends keeping the tank at 60°C to control bacteria such as Legionella, with an anti-scald mixing valve if needed to keep tap water around 49°C.
3. Electric tank: check the breaker (usually a double breaker) and reset it if tripped. If it trips again right away, leave it off and call a pro.
4. Electric tank: turn the breaker off, remove the upper access panel and insulation, and press the red reset button firmly. Replace the insulation and panel before turning the power back on. If it trips again, a thermostat or element has likely failed.
5. Gas tank: check that other gas appliances are working, and look at the status light on the gas control valve. Compare any flashing pattern with the label on the tank.
6. Power-vented gas tank: make sure the vent fan is plugged in and its breaker is on, and check outside that the vent opening is not blocked by snow or debris.
7. Older gas tank with a standing pilot: relight the pilot following the exact instructions on the tank's label. If it will not stay lit, the thermocouple likely needs replacing.
8. If hot water runs out quickly, flush the tank: turn the tank to vacation or pilot mode (or the power off), attach a hose to the drain valve and run it to a floor drain, open a hot tap upstairs, and drain until the water runs clear. The water will be very hot, so keep children and pets away.

If you smell gas, leave the house and call your gas utility's emergency line from outside. Never plug, cap or remove the temperature and pressure relief valve on the side of the tank, even if it drips; a dripping valve needs a technician. Scorch marks around the burner area, soot, or a carbon monoxide alarm mean you should stop using the tank and call a pro.

Call a licensed plumber or gas technician if water is leaking from the bottom of the tank (a sign the tank itself is failing), if the relief valve is dripping, if breakers keep tripping, or if the pilot won't stay lit after relighting. Most tanks last about 8 to 12 years; past that, replacement is usually better value than repair. Gas work in Ontario must be done by a TSSA-registered technician.