How to Flush a Gas or Electric Water Heater

Manufacturers of gas and electric water heaters recommend flushing the sediment from your water heater periodically. How frequent your heater needs flushing depends upon the quality of the water in your area. If the water in your area has a high mineral content you will have to flush more frequent.

WARNING: When you flush your water heater there is always the danger of being scalded. Be very careful and keep children and pets away during the flushing.

What is sediment, and why is sediment a problem?

Usually sediment consists of sand or other grit from a well, or any other material that has gotten into the water mains. Sediment can also come into your water heater when the local water company flushes their lines.

Over time, gas and electric water heaters can gather quite a bit of this sediment. This build-up can reduce the amount your water heater is able to hold, and can even create a variety of weird noises, and in general reduce the total efficiency of your water heater. The buildup of sediment at the bottom could even harden and eventually clog the drain valve.

The periodical cleaning of sediment from out of your water heater is not particularly difficult, and can often be taken care of without the help of a local plumber and will improve the efficiency of the water heater.

Before Flushing the Water Heater

If your water heater runs on gas, set the gas valve to Pilot. This is to make sure that the burners wont be coming on while you are busy flushing the water heater.

If your heater is an electric water heater be sure to switch off the circuit breakers. With an electric water heater, if the water level drops to a level below the heating elements, and the thermostat then turns the elements on, then your heating elements will burn out.

• Connect a garden hose to the drain valve at the bottom of your heaters tank. Make sure the outlet is in a safe area.
   
• Close the shut off valve on the cold inlet to the water heater.
   
• Carefully open the temperature / pressure relief valve at the top of the tank by lifting the lever. (leave the valve open)
   
• Open the drain valve at the bottom of the heater allowing the water to flow out through the garden hose.
   

If you see sediment blocking the drain valve, then try closing the temperature or pressure relief valve and turn the cold inlet valve back on to flush the sediment out. In some extreme cases the sediment blocking the drain hardens into large chunks that can block the drain valve completely. If this is the case, then you will need to wait until the whole system cools down before you can remove the clogs.

• Remove the garden hose from the drain valve, remove the valve if necessary.
   
• With a long screw driver try to break through the clog.
   
• Reconnect the hose back onto the drain valve.
   
• Close the drain valve at the bottom of the tank and remove the garden hose.
   
• Close the pressure relief valve at the top of the tank if it is still open
   
• Turn the cold inlet valve back on again.

Now you can open a hot water faucet in your house, and just let it run until no more air comes out of it. Then turn the heater back on, and with a gas unit re-light the pilot light if necessary.

External References

• How to Flush a Gas or Electric Water Heater (Chilipepper Appliance)
• How to Flush a Water Heater (eHow.com)