Flushing a tank water heater means draining a few gallons from the bottom valve to remove the mineral sediment that settles there. Arizona's hard water leaves more of it than most places, and heavy sediment makes the heater work harder, pop and rumble, and wear out sooner. Many homeowners can do it in about an hour or two, but the water is scalding hot and some heaters should not be flushed by an amateur.
Time: about 1 to 2 hours, mostly waiting. Skill: moderate.
Should you flush your water heater yourself?
Flush it yourself only if the heater is a standard tank model, you can reach the drain valve, and the unit is in good shape. Do not flush it if it:
- Is leaking, rusty at the bottom, or very old and has never been flushed
- Has a stuck or plastic drain valve that will not turn easily
- Is a tankless model (those need a different descaling process from the maker's directions)
If you are unsure, a plumber can check it first. Forcing a stuck valve can break it and leave you with a leak.
What do you need?
- A garden hose long enough to reach a drain, driveway or yard spot
- A bucket
- Work gloves
- A flashlight
How do you flush a water heater?
- Turn off the energy. For an electric heater, switch off its breaker. Never leave the power on while the tank is empty, because the heating elements burn out fast. For a gas heater, turn the gas control to the Pilot or Off setting as the label on the tank directs. Do not touch gas lines or fittings. If the label is unclear, stop and call a pro.
- Let the water cool. Wait an hour or two after shutting it off. The water is hot enough to scald.
- Close the cold water valve on the pipe feeding the top of the tank.
- Open a hot tap in the house, such as a kitchen faucet. This lets air in so the tank can drain.
- Connect the hose to the drain valve near the bottom of the tank. Run the other end to a spot where hot, dirty water is safe: away from people, pets, plants and the street.
- Open the drain valve and let the water run. It may come out cloudy or gritty. If it slows to a trickle, sediment may be clogging the valve.
- Stir the sediment. With the drain open, briefly turn on the cold water supply for a few seconds, then shut it off. Repeat a few times. Keep going until the water runs clear.
- Close the drain valve and remove the hose.
- Refill. Open the cold water valve with the hot tap still open. When water flows steadily from the tap with no air spitting, close the tap.
- Restore power. Only after the tank is full, turn the breaker back on, or relight the gas heater following the instructions on the tank.
How often should you flush in Arizona?
A common rule is at least once a year. In very hard water, some plumbers suggest more often. Ask a plumber what they recommend for your area. A water softener or filter reduces the minerals that cause the problem.
What are the signs of sediment?
- Popping or rumbling when the heater runs
- Hot water that runs out faster than it used to
- Cloudy or rusty hot water
- A heater that takes longer to heat
When to call a pro
Call a plumber if the heater leaks, the drain valve is stuck, you see rust in the water, the pilot will not stay lit, or the unit is old and you are nervous about disturbing it. Gas work and water heater replacement are for licensed pros. Here are local plumbers in the directory, with phone numbers:
Check any contractor's license at roc.az.gov. For tough cases, ask the helper to point you to the right business, or browse Phoenix businesses.
Questions people ask
Is it safe to flush a water heater that has never been flushed?
It can be risky. Sediment may have built up for years and a stuck valve can break or clog. If your heater is older and has never been flushed, ask a plumber to look at it first.
Do you need to turn off the water heater before flushing it?
Yes. Turn off the power or the gas first. An electric heater with an empty tank can burn out its elements in moments.
Why is there so much sediment in Arizona water heaters?
Valley water contains a lot of dissolved minerals. Heating water makes the minerals separate out, and they settle as scale at the bottom of the tank.
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