Water Heater Flushing and Draining

DEAR MIKE: We just moved into our house and have no idea what shape the water heater is in. I've been told it's a good idea to drain it periodically, but what steps do I need to take to flush it? -- Brad C.

DEAR BRAD: You should flush your water heater periodically depending on water quality, how much hot water you use, and whether you have a water softener. Manufacturers typically suggest flushing your water heater twice a year.

Mineral deposits are bad for a water heater. The deposits collect in the tank of a water heater and build up over time. In an electric water heater, they collect on the unit's heating elements and then flake off.
On a gas water heater, the deposits build up on the bottom separating the water in the tank from the fire at the bottom of the tank that heats the water. This makes the water heater inefficient and also causes it to gurgle or make a burping sound.

If you've ever cooked a heavy sauce you can watch it happen as it starts to boil, the sauce is so heavy you can't get it to a rolling boil. Instead, you get a slow large bubble that develops and finally burps out. Well, it's the same thing in the bottom of a water heater, except instead of sauce, it's sludge.

The long and short of it is that a water heater has to work longer to heat water. Additionally, the deposits will displace the water, effectively decreasing the amount of water the tank holds. So a 40-gallon water heater, for example, may be able to hold only 38 gallons.

So the fix is to drain the water heater.

It's best to flush the water heater periodically starting six months after it is installed. Your problem is that you don't know how long it has been since its last flushing.
If the water heater is, say, 5 years old, the first time you flush it may get rid of a lot of sediment, but may not remove the hardened deposits. Also, some of the deposits may be too large to fit through the drain opening.

To start, turn off the water heater. If you have a gas water heater, turn the thermostat dial to the "off" position, and if you have an electric heater, turn off the circuit breaker. Shut off the cold water supply by turning the knob clockwise on the valve located at the top of the unit.

Now get your trusty garden hose and screw it onto the drain valve at the bottom of the tank. Stretch the hose out so there are no kinks. For kicks, you can put the end of the hose into a five-gallon bucket to see the sediment pour out.

Open the drain valve and turn the cold water supply back on. The water will start draining out of the hose. Be careful as this water is very hot. When sediment stops flowing out and all you get is clear water, you can shut off the drain valve and restart the water heater.

You may have heard that it is better to drain the entire water heater, but if all you are getting out of the heater is clear water, it doesn't make much sense. If you choose to do this, don't turn on the cold water supply valve. Instead open the nearest hot water faucet to allow air into the system and the water heater will start to drain.

Like I said earlier, flushing the water heater may not help if the inside of the tank bottom is covered with hardened sediment that is stuck to the bottom.
You could try to drain the entire tank, unscrew the drain valve and jab at the sediment with a stiff wire, but this may do more harm than good. If you were able to free some of the debris, it may plug up the drain hole anyway.

It's best to stick with regular flushing about six months after installation.

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