Hi. We have a creepy knocking sound supposedly coming from the water heater. It is right by my kids bedrooms and it is very scary. It starts softly then it gets louder then softer. It is intermittent throughout the day. It doesn't seem to occur any differently when the water is on or off. I had a plumber come out and he thought it might be the water meter because he took a special stethoscope and stuck it into the ground near the water meter and he heard the same knocking noise. So, I called the city and they immediately came out and replaced the water meter. Unfortunately it made no difference:( Then the city water guy lifted the flap on the water heater to release some air out of the pipes, but that also made no difference. Last night, I heard the noise down the hall in the bathroom wall but it was much louder by the water heater. Do you have any ideas? Thanks.

Turn off the electricity/gas to the water heater and see what happens.

My guess is that there is a problem with the heater, not the water supply.

There's no risk in doing what I suggested, and the info you gain may help the experienced plumbers diagnose your problem more easily.

This is a long shot but I am guessing this is a gas water heater with a build up of minerals. If you kill the gas/electric like Rusty suggests the problem will stop but not be fixed. Have you tried flushing the tank via the drain plug at the bottom on the tank? Once again kill the fuel first and flush for about 10 minutes.

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Originally Posted by RustyFairmount

Turn off the electricity/gas to the water heater and see what happens.

My guess is that there is a problem with the heater, not the water supply.

There's no risk in doing what I suggested, and the info you gain may help the experienced plumbers diagnose your problem more easily.

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I forgot to mention that I did that too.:( I switched the fuse switch off for 2 days and we still had the same noises.

Could it still be a build up of minerals? I haven't tried to flush the water heater yet. How would I go about that or should I have my plumber do that?

Then you do have a electric water heater and not a gas oine?

The plumber who installed the water heater suggested that I switch the fuse off so I believe it is an electric heater.

I'm sorry if my questions sound silly, but are you sure the heater was off? I mean, after two days, you should have had absolutely no hot water in the house. How did you survive without hot water for bathing??

Assuming you did that and the heater was indeed off, and the noise continued, I'd suggest leaving the heater off and turning off the water supply to the tank. You should see two pipes leading into/out of the tank. One has a valve on it that looks like a water spigot. Turn that off. Does the sound go away?

How long ago was this tank installed??

Yep it is electric and I'm surprised your plumber did not offer more advice. I'd still recommend flushing the heater and it doesn't require a plumber, it is homeowner yearly maintenance that is easy. It may not solve your problem but it still should be done. Do you want the steps to follow?

The previous owners installed the water heater in 1999. The fuse box clearly marks the water heater fuse number so I can only assume that that is the correct fuse switch. That water heater heats only the kids bedroom area so we stayed in the other part of the house and I didn't notice the lack of hot water. I would appreciate knowing how to do the maintenance on the heater. The noise is really annoying. It wouldn't have anything to do with the air conditioner would it? That makes very strange noises as well. The noise is definitely the worst by the water heater. Thanks.

When ballengerb1 gives you the instructions on how to flush the tank, do all the steps, but Don't turn the tank back on (water, or power). See if the problem is gone.

I'm getting the feeling that there is absolutely nothing wrong with the tank. I'm betting that you'll still hear the noise even when it's off.

Do you know if your heater has heat trap nipples installed on the inlet and outlet? For long life and fewer troubles you should keep your heater clear of mineral build-up by flushing on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back togather the same way you took them out. Don't forget to flush it out every month. Your heater will thank you for it. Hope this helps, Tom

Look for a ball check valve on the water heater. I have two water heaters that do this. One is AO Smith. A ball or large weighted marble is bouncing up and down with the thermal currents rising. Drives me crazy and is scray to the kids. Take it out and insulate your pipes