Before you start
- Set the gas dial to pilot, or kill the breaker for an electric tank
- Shut the cold supply valve above the tank
- Attach a garden hose to the drain valve and run it to a floor drain
Steps
- Crack open an upstairs hot tap so air can enter the tank.
- Turn the drain valve and give the tank time to empty.
- Briefly open the cold inlet to stir up sediment, then let it drain again.
- Close the drain valve, refill with the hot tap open until water flows steadily, then relight or switch on.
Cautions
Water in the tank is hot. Let it cool for a few hours or wear gloves. Old plastic drain valves can break or leak after opening; if yours is old, have a replacement handy.
Rented heaters
If your heater is rented, check whether the rental company offers flushing as part of the contract.
If water from the drain valve is very rusty or the tank is over twelve years old, ask us to look before flushing.
Rather hand it over? Our plumbers handle gas water heater replacement and basement flood plumbing along with everything else on our residential plumbing list.