Plumbing question

[Hooverfb]

So I've noticed lately I've got a pipe knocking in the walls every few seconds.
Initially I turned off water heater, drained it (with cold water off), let it fill again and suddenly there was random air spurting out of different faucets from hot water line. So ran all faucets in the house on hot for 20 mins, eventually went away. Knock was gone for like 20 hours before it came back. Worth mentioning there was a bunch of sediment coming from each faucet at first.
I turned down the water heater to barely warm and I heard it softly every now and then but not bad.
Turned heater back up and now it's more prominent.

So should I try and flush the water heater leaving cold water on? It's been about 2 or 3 weeks of this that I've noticed. Possibly pressure from city line? Maybe turn off all water from the main line, drain from faucets, and run again if theres air trapped?

[Duckologist]

So I've noticed lately I've got a pipe knocking in the walls every few seconds.
Initially I turned off water heater, drained it (with cold water off), let it fill again and suddenly there was random air spurting out of different faucets from hot water line. So ran all faucets in the house on hot for 20 mins, eventually went away. Knock was gone for like 20 hours before it came back. Worth mentioning there was a bunch of sediment coming from each faucet at first.
I turned down the water heater to barely warm and I heard it softly every now and then but not bad.
Turned heater back up and now it's more prominent.

So should I try and flush the water heater leaving cold water on? It's been about 2 or 3 weeks of this that I've noticed. Possibly pressure from city line? Maybe turn off all water from the main line, drain from faucets, and run again if theres air trapped?

It's free to try all of dat!

[Hooverfb]

It's free to try all of dat!

Very true lol.

[eradicator]

How old is the house/pipes? I'm certainly no plumber but may help some of the experts on here diagnose it. Also, how old is water heater?

[TexasBob]

Sure its a pipe and not the water heater? When ours (gas) needed to be replaced it made some awful noises. Had a lot of sediment in it and would clunk etc when heating

[Hooverfb]

I cant pull off landrovers multiquote greatness, but water heater is probably 5-8 years old. House was built in the 80s I believe. All copper piping soldered together.
No weird noises at the water heater itself, just a pipe that periodically knocks every 3 seconds or so when it starts to. It does not knock if I run hot water (as in will also stop doing it if it was occurring at that moment).

Forgot, yes it is a gas heater.

[OldRiverRat]

I’d say it’s the water heater
Had similar issues with mine and just replaced it and the knocking went away.


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[Mike Fangman]

Maybe try tying in a hammer arrestor, in the line that is knocking, if you can get to it from the attic.

[Paycheck]

I would try to add a water hammer arrestor. Something like this:
https://www.grainger.com/product/11Y...g!663156281672!

[Stuck]

Does it knock for a little while then quit or knock continuously while the hot waters running?

[Hooverfb]

Does it knock for a little while then quit or knock continuously while the hot waters running?

Knocks every 3 seconds for a few minutes then goes away. Will come back sometime later at random.

[Stuck]

Knocks every 3 seconds for a few minutes then goes away. Will come back sometime later at random.

Sorry, forgot to check back. If you haven’t located the problem it sounds like it could be the hot water pipe going though the top plate or possibly a stud. When the hot water hits the pipe it expands a little bit and you can get a knocking sound. Easy fix IF you can locate the point it’s happening and have access to it.

[hpdrifter]

How hot is the hot water?

Sounds like your thermostat is not cutting off soon enough.

[Radar]

Might be Sancho wanting out, open closet.

[double bogey]

These water hammer devices are pretty simple. All they do is provide a cushion of air to smooth out the hammer.
A tee, an piece of tubing, and a cap is all you need to build one. If you have 6" to 10" of 3/4" tubing and soldering skills, you buy a tee and cap at your favorite hardware store and install it near the water heater outlet.
I have used them a bunch when the water pressure was too high for a cooling tower float valve design pressure.
Mine at home hammer a lot when washing clothes in warm or the hot cycle.