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How To Flush A Residential Water Heater


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CAUTION: Flushing your water heater may put you at risk of being scalded by hot water. Please be careful when working on your water heater.

Sediment gathering inside the water heater can cause a number of problems. Once the sediment settles to the bottom of the tank, it can harden. In gas water heaters, this will create a buffer between the bottom of the tank that is heated by the gas burner and the water itself. The heater will not operate at its design efficiency and you may notice some rumbling noises. If enough sediment accumulates, it will eventually clog the drain valve.

In electric water heaters, the same accumulation occurs. This sediment will stick to the heating elements and form a whitish scale. The scale on the heating elements acts as the same buffer in the gas water heaters. Theheat transfer from the elements to the water become less efficient as the scale build up becomes thicker. Like the gas water heater, if enough sediment accumulates at the bottom of the tank, the drain valve will become clogged.

Accumulation of sediment in the bottom of your water heater can be controlled with periodic flushing. Flushing will not remove all traces of sediment; however a routine flushing regime will prevent excessive sediment build up inside your water heater.


  • 1. Turn OFF power to the water heater at the circuit breaker (electric heater)

or main gas line (gas heater).

2. Fasten a length of garden hose to the drain valve at the bottom of the heater. Put

the other end of the garden hose in the nearest floor drain or snake it outside the home.

3. Close the shut off valve at the cold water inlet line.

4. Open the temperature and pressure relief valve at the top of the heater. Now open

the drain valve and allow the water to drain. You will probably notice some small white

particles (called scale or sediment) during the early stages of the flow.

5. When the water stops, close the drain valve and remove the hose. Also close the

temperature and pressure relief valve at the top of the heater.

6. Open a hot water faucet somewhere in the home. Open the shut off valve at the

cold water inlet line. You will hear the heater start to fill.

7. When you have a steady stream of water from the open faucet, turn the faucet off.

8. Turn ON power to the water heater at the circuit breaker (electric heater) or main

gas line (gas heater). Allow the water heater to recover. Check the drain valve one

more time to make sure it is tight.

id="left">Homeowners should flush their heaters at least every six months. Some areas of the country with hard water may need to be flushed more often. After flushing your heater a few times you will discover the schedule that is right for you. Some areas may require MONTHLY flushing due to the water conditions, thermostat setting and amount of hot water usage by the consumer.

It is impossible to make a ‘one size fits all’ maintenance recommendation for every heater. Each water heater has its unique applications once it becomes installed in your home. Flushing your water heater of sediment should be a scheduled maintenance event.

RheemLogo.gifThis Rheem technical service bulletin is provided through special arrangement between Rheem Manufacturing Company and The Inspector's Journal.

To obtain a printer-friendly version of this article for your customers, click on this link.

You can find additional plumbing-related topics at TIJ's Plumbing Forum or discussions about other inspection-related topics on TIJ's Other Forums.

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