Homeowner guideHow-to
Draining Sediment From a Tank Heater
Flushing a tank water heater once a year removes sediment that makes it noisy, slow and shorter-lived. It takes about an hour and basic tools.
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The short version
- A hose that stretches from the tank to a floor drain or out a door.
- A flat screwdriver or wrench for the drain valve.
- Gloves, since the water will be hot.
- A bucket.
Before you start
From the van: If the drain valve is plastic and very old, it may break or leak after opening. Have a replacement on hand or call us.
Steps for a gas tank
- Turn the gas control to Pilot or Vacation.
- Shut the cold inlet valve on the pipe feeding the tank.
- Connect the hose to the drain valve at the base and run it to a drain.
- Crack open a hot tap on an upper floor so air can enter.
- Open the drain and wait while the tank empties out.
- Open the cold supply briefly to stir up sediment, then close it again. Repeat until water runs clear.
- Close the drain valve, remove the hose and open the cold supply to refill.
- When water flows steadily from the open hot tap, close it.
- Return the gas control to its normal setting.
Steps for an electric tank
Turn off the breaker before draining. Never power an electric tank while it is empty; the elements can burn out in seconds. Follow the same steps, and only switch the breaker back on after the tank is full and air is out of the lines.
What to watch for
- Lots of sediment: flush more often.
- Rusty water that never clears: the tank may be corroding.
- Leaks at the drain valve: replace it.
Tankless heaters
Tankless units need descaling rather than flushing, using a pump and a descaling solution through service valves. Follow the manufacturer's instructions or book a service visit.