Our plumbing has recently started something alarming. When flushing the master bath toilet (the last stop in the line), we often (but not always) get a long series of groans and bangs from the pipes under the house, which continues until the tank fills. Sometimes the noise can be stopped by opening a faucet.
Problem only happens with cold water, and only in the master bath.
My handy-dandy home maintenance guide book suggests checking to see if the pipes have come loose (I looked under the house; everything seems secure). It also suggests shutting off the main valve, and draining all water from all faucets, then re-opening the main valve (check…no help).
Hmm, I was going to suggest air in the lines. Are you sure you got ALL the water out. That would be shutting off the main, and open not only all the faucets, but also turn the shower knobs, flush the toilets, any spigots outside the house and for good measure you could even do the hot water side (including the water heater) but that’s probably not needed.
It is water hammer phenomenon. Only with the flush valve? If so check to see if float is bouncing. Maybe a new water filling valve would solve the problem.
A surge supressor installed at or near the end of the cold water line at the commode connection or under the wash basin shoud also be considered.
It sounds like the float valve in the toilet. Next time it happens, take the tank top off and manually lift the float, if it stops the noise you have found your problem. Replacing the the valve should end the noise.
BTW never drain a water heater without turning off the power to it first. The water heater is very unlikely to have any thing to do w/ this problem.
The Google ads at the bottom brought me to a site that addressed water hammer…but the definition there said that “water hammer” was a loud banging noise when water is suddenly turned off. While I think we have had that problem to some degree in the past, this problem is (a) not so much a “banging” as a “groaning”; and (b) starts when the water is turned on.
This sounds promising…but doesn’t lifting the float valve just stop the tank from filling? I already know that the noise stops when the tank stops filling.