Loud humming/groaning noise when toilet flushed - a problem?

Ash_Pole

When the toilet is flushed there's a loud humming/groaning noise when the cistern starts refilling. It's not from the toilet itself it's from where the pipes are behind the bath. I assume it must be water moving through the pipework.

It's been doing this for a while now, maybe over a year, but does seem to have got more noticeable recently. It's worse when it's not been flushed for a while. First thing in the morning it's loud but flush again 10 minutes later and there's no noise.

What causes this and is it something to worry about?

Grenage

I am going to take a guess at the inlet mechanism for the cistern; probably a washer or the like.


The fill valves are quite cheap and easy to replace.

Ectophile

I've had that before on a toiler cistern that was plumbed in at mains pressure (rather than a water tank in the loft). It happened just as the tank was nearly full and the valve was shutting off.


If you have a service valve in the pipe leading to the cistern, then turning it partially closed might help. Or it might not.


I found that adding more pipe clamps on the pipe run up to the cistern, to hold it rigidly to the wall, helped a lot.

Hoploz

My toilet has just started doing this since installing a new water system and it's now mains fed instead of tank. I'm assuming it isn't doing any harm??

bris

To much pressure for the valve. Turn the isolating valve slowly in the closed direction until the noise stops.

molerat

Could simply be the washer in the ball valve is worn out or there is some grit stuck in it, usually a 2 minute job to replace.