How to look after your water heater

To look after a tank water heater, first find out whether you rent or own it. Then test the temperature and pressure relief valve and flush the tank once a year to clear sediment, keep the tap water at no more than 49°C, and keep the vent and air intake clear. If you rent it, the rental company looks after repairs, so call them before you do anything more than the checks below.

Rent or own?

Many Ontario homes rent their water heater. Renting includes installation, repairs, parts, labour and replacement if the tank fails. If you rent, call the rental company for anything beyond the simple checks in this guide, and don't open, drain or replace the tank yourself without asking them. If you own it, you pay for repairs once the warranty runs out, and the rest of this guide is yours to do or hire out.

Our water heater cost guide compares renting and buying, and covers how to end a rental.

iSource: Enercare, "Water Heater Rental vs. Buyout".

What to do, and how often

iSources: Home Depot Canada, "Best Water Heaters for Your Home"; Enbridge Gas, "Appliance safety".

Test the relief valve

The temperature and pressure relief valve near the top of the tank lets water out if the tank gets too hot or the pressure gets too high. A pipe runs from it down toward the floor. Home Depot says to test it once a year.

1. Put a bucket under the end of the discharge pipe.
2. Lift the valve's lever for a moment. Hot water should run out of the pipe. Keep your hands and feet clear: the water is very hot.
3. Let the lever snap back. The water should stop.

If nothing comes out, or the water keeps running after you close it, call a licensed contractor (or your rental company).

Flush the tank

Sediment and scale settle at the bottom of a tank over time. Home Depot says to flush the tank once a year. If you're not comfortable working with hot water and gas or electricity, hire a plumber. Alberta Health Services gives these steps when the manual doesn't:

1. Turn off the cold water valve near the top of the tank.
2. Turn off the heat: for an electric tank, switch off its breaker first; for gas, turn the gas control to pilot or the lowest setting.
3. Attach a garden hose to the drain valve at the bottom of the tank, and run it to a floor drain.
4. Open a hot water tap on the main floor or higher, to let air into the tank.
5. Open the drain valve and let the tank empty. It can take 20 to 60 minutes.
6. Stir up the sediment: turn the cold water valve on and off three times, and open and close the drain valve three times. Repeat until the water from the hose runs clear.
7. Close the drain valve, then turn the cold water back on to refill the tank. Close the hot tap once it runs steadily.
8. Turn the heat back on, and check the drain valve for drips.

Never force the drain valve open or closed. With an electric tank, never turn the power back on while the tank is empty: it can damage the heater.

iSources: Home Depot Canada; Alberta Health Services, "Flushing your water heater tank" (current as of 2 May 2025).

Set a safe temperature

Water from any tap in your home should be no hotter than 49°C. At 60°C, hot tap water can give a child a third-degree burn in about a second; at 49°C it takes about 10 minutes.

• Gas and oil water heaters: set the thermostat to 49°C, or the Warm or Medium setting. Don't go lower, because cooler water in the tank can let Legionella bacteria grow.
• Electric water heaters: keep the tank at 60°C or higher. A plumber can fit a mixing valve so the water at your taps stays at about 49°C.

To test it: run the hot tap at its hottest for two minutes, fill a cup, and hold a meat or candy thermometer in it for 30 seconds.

iSource: Parachute, "Hot tap water" (last reviewed 7 August 2025).

Keep the vent and air intake clear

A gas water heater burns fuel like a furnace does. Keep dust, lint and dirt away from the air intake at the bottom of the tank, keep boxes and anything that burns away from it, and keep its vent clear. Have a gas water heater looked at regularly by a certified heating contractor, and make sure your home has working carbon monoxide alarms: next to each sleeping area and on every storey.

iSources: Enbridge Gas, "Appliance safety"; Government of Ontario, "Carbon monoxide safety".

Signs it's time to replace it

• Water leaking from the tank itself.
• Rusty or discoloured hot water.
• Not enough hot water, or hot water that comes and goes.
• New noises from the tank.
• Age: Home Depot suggests thinking about replacement after 10 to 15 years.

If the tank is leaking, turn off the water heater, shut off the cold water valve or your home's main water supply, and call a plumber or your rental company.

iSources: Home Depot Canada; Enercare.