Flushing a Tank Water Heater

Why it matters here

Water in Durham carries dissolved minerals. When it is heated, some of those minerals settle as sediment at the base of the tank. On a gas heater, sediment forms a layer between flame and water, so the burner labours and the tank can rumble or pop. On an electric heater, the lower element will get buried in scale and burn out. Annual flushing slows all of this down.

Step by step

1. Turn off the heat source. On gas models, turn the control to pilot or vacation; on electric models, switch off the circuit breaker.
2. Let it cool. Wait a couple of hours, or use caution with hot water.
3. Close the cold inlet valve above the heater.
4. Connect a hose to the drain valve and lead it to a floor drain or out through a door.
5. Open a hot faucet upstairs, which lets air into the tank.
6. Open the drain valve. Drain until the water runs clear. For a quick flush, open and close the cold valve briefly to stir up sediment.
7. Refill. Close the drain, open the cold valve and let the tank fill until water flows steadily from the open hot faucet.
8. Restore heat. Turn the gas back on or switch the breaker, only once the tank is full.

Mistakes to avoid

• Switching on an electric heater before it is full, which ruins the elements.
• Forcing a plastic drain valve that will not open. Old valves can break and leak.
• Flushing a heater that has never been flushed in many years without a plan. The valve may clog with sediment.
• Flushing a rented heater if the agreement says the company does it.

When to call a plumber

Phone whether the drain valve leaks after flushing, if the tank keeps rumbling, or if the water stays rusty. Those can point to a failing tank or anode. We can install a brass drain valve, check the anode rod and advise on the heater's life. A clogged floor drain can be cleared through basement floor drain cleaning. For flood protection, consider a battery backup sump pump. Then keep your drains clear with our list of what never goes down a drain.