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Noisy hot water tank

For about six months now, my hot water tank has been making loud noises whenever a hot faucet is turned on. The sound is not in the pipes, it's in the hot water tank. It makes a loud clunking sound and also when the gas burner is on to heat the tank and someone uses hot water, the tank makes a loud bubbling sound. I thought it was air in the tank or pipes, but I can't seem to get any air our of the faucets or out through the pressure release. I've also tried to drain some water out of the tank, but nothing has helped.

Re: Noisy hot water tank

Mine does the same.

What you are hearing are small explosions of steam. This is a result of the way the boiling point is affected by changes in pressure.

This develops because, over time, the walls of the water heater become encrusted with deposits of scale from hard water. Pockets of water get trapped in the scale. The pockets become pressurized and go to a higher temperature than boiling, but, because the water heater is under pressure, the boiling point is higher and the water pocket does not vaporize--yet.

Then, you lower the pressure in the WH by opening a faucet. Suddenly, the overheated pocket of water explodes into steam, and you hear banging, rumbling, etc. Also, as the burner continues to raise the temperature, the pockets get hot enough to burst into steam.

This happens especially toward the end of the WH's re-heating cycle, when the temperature is reaching its maximum.

You can try de-scaling the tank, but you may decide to live with it when you realize that nothing bad is going to happen. It's not dangerous--just annoying. (And a loss of heating efficiency, since the scale buildup reduces the efficiency of heater.)

Re: Noisy hot water tank

It's good to know that my problem isn't catastrophic, but it is VERY annoying. The water heater is directly under my bedroom, so when someone take a shower late at night, I don't get much sleep.

You mentioned that I could "descale" the tank. How can that be done and how successful is it?

Thanks for your help and advice!

Re: Noisy hot water tank

Descaling is messy, time-consuming, and not very effective.

It means emptying the tank, refilling with a dilute acid, like vinegar or some proprietary product made for the purpose, letting it set--the longer the better--and then flushing the tank thouroghly. A real pain. And the scale will only be reduced, not eliminated. If you've ever tried to descale a tea kettle, you know what I mean.

Re: Noisy hot water tank

It does sound like a lot of pain for little benefit and that doesn't even cover the complaining that I'll get from my family because they won't have hot water for the better part of a day.

I guess I'll just live with it...

Thanks again for your good advice!

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