Waterhammer

[Juan C. Reyes]

Howdy,

I live a condo (4 condos per building). In the last several months, our building has been exhibiting this odd "hammer/banging" noise coming from the plumbing. At first, I didn't know what this was, but now I suspect this is water hammer.

I'm trying to better understand how this could happen suddenly, since this just started a few months ago (with no noise for several years prior). We did have one unit do a major bath/kitchen remodel (shortly there after is when the waterhammer started). Other than that, I'm not sure what could cause it. Water pressure was found by our home owners association to be OK. Is this due to loose pipes in the walls (our four units share the plumbing system)? Would a water arrestor at the main (main for the 4-unit building) solve this problem? Any theories on causes and potential solutions would be appreciated.

Thanks.

[John Grabowski]

The pressure reducer for your unit has gone bad. Call a plumber to have it replaced.

[Speedy Jim]

It could indeed be loose piping rattling. But it usually takes some cause to precipitate the rattling.

The remodel is certainly suspicious as to timing.

If the sound is one single "BANG!" quick-closing valves such as dishwasher/washing machine solenoids may be to blame.

If the sound is more like machine-gun firing, could be a toilet fill valve closing or a shutoff valve with a loose washer (or valve only partway open).

I bet you'll need to enlist the co-operation of the unit owner who had the work done to narrow the source down.

A hammer arrestor on the water service is too far from the cause (probably) and likely would have little effect.

Jim

[Blue]

After puzzling over water hammer I simply drained the water heater and refilled it, end of problem. Seems that reduced headspace at the top of the WH was causing it. Draining and refilling it put the headspace back in action.

[Luke]

[snippage]

Does the "hammer/banging" occur when a faucet is shut off or a toilet finishes filling? Or does it occur when water is running?

[Juan C. Reyes]

Good question...it doesn't happen when I run/turnoff any faucet from my unit. I seems to be coming from another unit; unfortunately, I don't know which one.

[Luke]

[snip bottom quotes]

Bummer. Is it just one bang, or is it continuous (or intermittently continuous) banging? Can you further describe the noise, and give any other details like time of day?

[Juan C. Reyes]

A short burst (like a machine gun) Usually happens either around noon or evening At one point when it happened, I quickly reach under my kitchen sink to feel which pipe was vibrating (not moving but vibrating). It was the hot water line.

[Ron]

[Luke]

[snip]

See Speedy Jim's post, above, where he says:

"If the sound is more like machine-gun firing, could be a toilet fill valve closing or a shutoff valve with a loose washer (or valve only partway open)."

If you're right about the hot water, it's not a toilet [or shouldn't be ;-)], more likely a faucet washer or valve stem, or a dishwasher or washing machine solenoid or shut-off valve.

You'll need to knock on doors and politely explain the situation to find the "culprit", and/or enlist the aid of management or your condo association. It may be the folks in the "guilty" unit haven't gotten around to reporting the problem yet or don't realize (amazing as it seems!) they have a problem and will be grateful to you. Or not ;-).

[Juan C. Reyes]

Just posting back my results:

We recently had the association plumber check out this problem while all 4 homeowners were present. Turns out the waterhammer was being caused by 1 homeowner whose hot water shutoff valve (to the kitchen sink) was only partially opened....something like 15% open. Anyways, plumber found and corrected problem within about 10 minutes. No more waterhammer. Homeowner had no idea she was causing this problem.