How to Identify a Water Hammer

[farmerjg]

I tried doing a search and didn't find anything specific to my query, so apologies if it has been answered and I just don't understand what I'm asking.

At random times of the day I will hear a water hammer. It always emanates from the same side of the house. In fact, it sounds like it's coming from the water main supply to the house. There is no specific act that instantaneously causes the water hammer (ie-not caused by faucets, toilets, washing machine, dishwasher, etc). It's not even some consistent finite time after using devices with water. Could it be the water heater filling maybe?

Anyway, I digress, I've had the town come out and check their check valve and all of their equipment and they've said it all looks good.

To my point, is it possible that water hammer is not caused by any specific "appliance" but rather it's a function of the whole system? If it's a system level issue, can an arrestor fix that? Where would the arrestor even be installed in that scenario?

Any help is appreciated. I'm sorry if I've said things wrong or didn't explain well.

 

[phishfood]

Water hammer usually occurs when fixtures have water flowing to them and are suddenly shut off. Inertia makes the water want to continue flowing through the pipe, but can't because the fixture isn't letting water out. The weight of the moving water causes really high pressure spikes in the piping, the piping reacts by moving around rapidly, and bangs against things.

So, if the hammer is not caused by one of your fixtures being shut off, that is a little odd.

 

[farmerjg]

Thanks for your feedback. I've worked in manufacturing facilities before that would occasionally hammer (really scary when a 36" cooling line hammers right above you!!!!) so I'm familiar with the noise, otherwise I don't think I would have known what it is.

But yes, I agree, I think it's really weird that it doesn't align with water usage. That's why I don't know how to start diagnosing what it is and where it's coming from. Could a spike in pressure from the city possibly cause this? Do they make arrestors for supply lines like that? Would a regulator ensure consistent flow?

 

[plumber78]

What kind of water piping do you have? Copper, CPVC, PEX?

 

[farmerjg]

PVC but I believe I've fixed the issue.

I said it wasn't tied directly to water usage, well....as far as I knew that was kind of true. I had a toilet in the basement with a leaky flap. I don't know enough about toilets, but the tank was emptying and somehow causing my hammer. I shut the water off to the toilet three hours ago and it hasn't done it since. I was talking to a family friend, who does plumbing on the side, and I told him it was getting progressively more frequent and he immediately said toilet flapper.

Looks like that was the fix. Thanks for everyone's help!