hot water jackhammer

Mavster

I have a domestic recirculating hot water system that jackhammers in a very strange way.

It only happens every few weeks, only in the morning, happens 5-15 times for a few seconds each with 10-60 seconds in between.

It does not appear to be the recirc pump and continues even when several taps - shower, sinks, etc are running.

Could it be the water supply coming into the house?

replies greatly appreciated.

Weezbo

sometimes an ST-12 will help

by installing one in the cold water inlet side after the check valve .

Mavster

yep - have an expansion tank

Thanks for the reply, Weezbo.

Yep, I have an expansion tank installed.

John Starcher_4

Does it only happen when....

....you have a faucet open?

Mavster

It appears to start when nothing is open and continues even when things are open including showers. It does not seem to match open or closed valves.

John Starcher_4

OK, then....

...that rules out a faucet washer 'flapping' loose inside a valve. Is there a check valve in the recirc. line that might be chattering? To test, shut off your recirc pump and see if the noise stops.

Steamhead (in transit)

Check your toilets

for a slightly leaking flapper. Sometimes, the ballcock in the toilet tank sets up a standing wave oscillation that can sound like it's coming from everywhere and nowhere.

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Larry Weingarten

Get a ...

... pressure gauge that reads up to 160 or 200 psi and put it on a bibb you can get to quickly. I once had to find the cause of a similar noise and it turned out to be the local water company pumping station. Pressure was falling to less than zero when their pressure pump shut down for a second or two. Without a gauge I'd still be looking in the house for the problem ;~) The water company didn't know they had a problem.

Yours, Larry

eluv8

check valve

sometimes if the flow is low, or just right the check valves can cause some funny sounds in the pipes. especially the swinging type.

Mavster

thanks to all for the replies

data I did not make clear....I can hear the jackhammer sounds in different places around the house....it moves around. in the pex piping....in the ceiling above a bedroom, near a bathroom, over a shower....

Mavster

Data I did not make clear....I can hear the jackhammer sounds in different places around the house....it moves around. in the pex piping....in the ceiling above a bedroom, near a bathroom, over a shower....

Ed_26

Jackhammer?

Got a woodpecker in the attic or pounding on your walls/chimney? (had one once fell into my chimney!)

Bob Knebel

PEX Creepage?

The original poster said ... "It only happens every few weeks, only in the morning, happens 5-15 times for a few seconds each with 10-60 seconds in between." AND "I can hear the jackhammer sounds in different places around the house....it moves around. in the pex piping....in the ceiling above a bedroom, near a bathroom, over a shower...."

Just a guess here but maybe your recirc pump is timed to come on in the morning (after the hot-side PEX has cooled off at night) and then the PEX starts "creeping" with expansion after seeing the hot water. Did your plumber isolate the PEX lines well from the floor joists and wall framing?