07:29PM | 05/13/04
Member Since: 09/11/02
78 lifetime posts

I have a very old water heater (installed c. 1965) that is in excellent condition and has worked wonderfully. I wonder, though, about the water quality. Both my husband and I have been sick more often since moving into our house, and I wonder if water from the hot water heater is to blame.

Does anyone have experience with this? What can happen if a water tank isn't cleaned over many years?

Also, how does one clean out a water heater?

Many thanks!


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Jim D

11:51PM | 05/13/04
Member Since: 01/06/01
342 lifetime posts
Kellyyouse - hi, I don't have any experience with illnesses traced back to a water heater, but I guess it's possible. The only way to know for sure would be to take water samples from the hot and cold sides and get them tested. Depending on where you live, your county or city health department should be able to direct you to the right place.

As far as cleaning out a water heater, normally it's fairly simple. Cut off the power to the heater (assuming it's electric), and close the valve that supplies water to the heater. There should be a drain valve (large, can be turned by hand) near the bottom of the unit, which should accept a standard garden hose. You can connect a hose there, route the hose to a suitable place to drain off the water, and then open the valve. You may see sediment coming out - that's normal and it's good to get it out of the tank. Once it's totally drained (which can take an hour or more), you can then close the drain valve, disconnect the hose, re-open the water supply to the heater, and let it totally fill up BEFORE you turn the power back on. Otherwise, you'll burn out the element(s) by applying power before the tank is full of water. And, since the supply water will be cold, you can expect it'll take a while to heat all the water in the tank.

I'm sure the real plumbers will post here to correct anything I've outlined incorrectly. One thing I'm not sure about would be getting air into the water shouldn't introduce any air into the hot water line by following my steps above. What you can do to make sure the hot water tank is filled and to get air out of the lines would be to go and open the hot water taps on all faucets in the house once you're pretty certain the tank is filled. Even though the water will be cold, it'll flow from the tank to each faucet and should purge any air in the lines.

I've been told you should do this probably once a year on older water heaters as a preventive maintenance thing. I hope this is helpful to you - good luck! Jim D/Heathsville, VA


02:01PM | 05/14/04
Member Since: 09/11/02
78 lifetime posts
Jim D,

Thanks very much for your reply. Our water heater is gas powered, not electric, so can I assume that it's okay to leave the gas on, or should that be turned off before draining the tank?

Again, much appreciated!


Gary Slusser

09:01AM | 05/16/04
Member Since: 02/17/04
112 lifetime posts
You always trun off the power and fuel to any water heater you are about to drain. Not doing so can cause serious and expensive problems.

Ligionella and other types of bacteria can thrive in a water heater that has a temp of less than 140f. Legionella is dangerous and it is being found in many water heaters.

To drain a heater you need to keep the hose end level to or below the level of the drain valve or you will leave a substantial amont of water in the tank. You have to allow air into the tank or the water will not drain. Open a hot water faucet or the T/P valve. If you use the T/P valve be prepared to replace it due to leakage after you close it. The T/P valve should be replaced every so often anyway, so do it as part of draining the heater.

When you drain the tank, which should be done annually, it's an excellent time and oppportunity to flush it. I flush by fully draining and then once the water stops flowing I turn on the cold water feed line fully and count slowly to 5 and shut it off. Then allow all the water to drain watching for dirty water as the water stops flowing; usually there is a lot if the house has its own well. I then repeat the cold feed water part until I can't get anymore dirty water out of the tank. Then close the drain valve, turn on the cold feed line and fill the tank and open the hot water at a tub or large utility sink to purge the air from the tank and hot water plumbing. Once the water flows from the tub or sink faucet, shut it off. Run all other hot faucets to purge the air and turn on the power and fuel and relight pilot lights if needed.

If I'm dealing with hot water odor (all are caused by bacteria) I santitize the heater. That invloves adding bleach to the water in the tank before draining the tank. I use the T/P valve or its mounting hole to do that.


Quality Water Associates

erik peterson

02:36PM | 05/17/04
Member Since: 06/23/03
223 lifetime posts
There is no value in trying to clean such an old heater. Annual or bi-annual cleaning can extend the life of the unit but must be done from the time of installation. Junk the old heater particularly if you suspect it of harboring microbes....A new heater will produce not only more hot water but will do so using less fuel (gas or elect) erik
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