Water hammer

[Hobo Bill]

2019 Reflection 337RLS. Last couple of weeks hearing a clunking noise - clunk clunk - when I turn on water - either hot or cold, or toilet. I am full timing in the same place for the last few months and on city water. Sound coming from behind the hutch where the hot water tank and water panel is. Doesn't happen every time, only happens a few times per day. Sounds like water hammer from taking in air somewhere, but I don't know where that would be from. Any ideas ??

[Second Chance]

"Water hammer" happens when you turn the water off abruptly. Is the sound happening when you turn the water on or off? Also, air is more compressible so usually reduces water hammer - that's why many plumbers put the little capped-off pipe above the faucet manifold for an air trap. On the other hand, sometimes reducing the pressure in the hot water heater will cause some air bubbles to rapidly form. That's usually a one or two second sound rather than a single "rap."

Rob

[Hobo Bill]

"Water hammer" happens when you turn the water off abruptly. Is the sound happening when you turn the water on or off? Also, air is more compressible so usually reduces water hammer - that's why many plumbers put the little capped-off pipe above the faucet manifold for an air trap. On the other hand, sometimes reducing the pressure in the hot water heater will cause some air bubbles to rapidly form. That's usually a one or two second sound rather than a single "rap."

Rob

Happens as soon as I turn on the water. It goes clunk clunk, just as you would say it. No other strange noises.

[Second Chance]

Happens as soon as I turn on the water. It goes clunk clunk, just as you would say it. No other strange noises.

My guess is, then, that it's expansion in the hot water heater. If that's the case, it's nothing to worry about. Is the water pressure at the park high and are you using a water pressure regulator?

Rob

[Hobo Bill]

My guess is, then, that it's expansion in the hot water heater. If that's the case, it's nothing to worry about. Is the water pressure at the park high and are you using a water pressure regulator?

Rob

Yes, using a water pressure regulator set at 45 psi and yielding 45 psi. Campground pressure ranges from 50-60. Would the expansion of the hot water heater also be as a result of flushing the toilet ? Thank you for your help and if you have other questions or comments let me know.

[Second Chance]

Yes, using a water pressure regulator set at 45 psi and yielding 45 psi. Campground pressure ranges from 50-60. Would the expansion of the hot water heater also be as a result of flushing the toilet ? Thank you for your help and if you have other questions or comments let me know.

Yes - if it causes a drop in pressure on the input side of the water system. If you watch the gauge on your pressure regulator while someone opens a cold faucet or flushes, you'll probably notice a dip in the needle.

Rob

[AZMike]

Happens as soon as I turn on the water. It goes clunk clunk, just as you would say it. No other strange noises.

I've had it happen with old (especially hot) water faucets with bad gaskets/washers. In fact, it's happening now in the bathroom that I haven't gotten to remodel yet.

[traveldawg]

Isn't there suppose to be some air space in the water heater such than when it is filled there is some air in the top of the tank to allow for expansion? Isn't there a particular way to fill the water heater to establish (or re-establish) that air pocket? Could lack of an air pocket cause the noise?

I like the idea about the pump being on.

[Second Chance]

Isn't there suppose to be some air space in the water heater such than when it is filled there is some air in the top of the tank to allow for expansion? Isn't there a particular way to fill the water heater to establish (or re-establish) that air pocket? Could lack of an air pocket cause the noise?

I like the idea about the pump being on.

There will be some air at the top of the water heater, but that doesn't stop water from "boiling" when the pressure is reduced by opening a faucet. I don't think it's water hammer here, from what @Hobo Bill is describing.

Rob

[Always Learning]

2019 Reflection 337RLS. Last couple of weeks hearing a clunking noise - clunk clunk - when I turn on water - either hot or cold, or toilet. I am full timing in the same place for the last few months and on city water. Sound coming from behind the hutch where the hot water tank and water panel is. Doesn't happen every time, only happens a few times per day. Sounds like water hammer from taking in air somewhere, but I don't know where that would be from. Any ideas ??

You have had some good responses here. I don’t know what the clunking could be but here are a couple of thoughts.

My experience from living in a fifth wheel for the last eight years is that after the water heater finishes heating there will be a higher pressure in the water system and the first faucet, hot or cold, opened will surge for a second or so. I have lived in two different rigs and both had the after heater shut off surge so I suspect it is normal. It becomes obvious when dry camping and only turn the water heater on for showers. I always figured the water in the water heater expanded and increases the pressure in the system causing the temporary surge of water. This may be related to your noise.

As someone else pointed out the rv water heaters have and need an air pocket in the top of the tank to work correctly. The water heater manual for my 2020 heater has a procedure for re-establishing the air pocket at the top of the heater. Check your manual. It goes something like, cool the heater off, turn off water, open a faucet, then open the pressure relief valve to let the heater suck in air. I do this on mine to keep the heater from weeping or dripping from the pressure relief valve.

If re-establishing the air bubble in the heater does not fix the noise then you need to take out the back basement wall and try to get it to make the noise while you are down there. You might have a piece of PEX knocking against something.

I think water heaters in RVs probably make all kinds of strange noises. In my old trailer the water heater would pop and groan, squeal and make all kinds of strange sounds.