pipes that sound like a fog horn

[parietal]

So everytime someone flushes the upstairs loo in our house, the pipes make a sound like a fog horn. A big low sound that varies in intensity but it lasts 2 mins (as long as it takes for the cistern to refill) so I am pretty confident it must come from the inflow pipes to that cistern. This started suddenly about 2 weeks ago, having never happened in the previous 8 years.

some other info

• house was built in the 70s and extensively rebuilt by previous owners 10 years ago
• other pipes (including the sink & shower in the same room) don't make a noise
• the sound seems to come from the ceiling above the bathroom, which would make sense in terms of pipes. But all the pipes are concealed and I don't much want to pull the ceiling apart.

What can we do to stop this? And could it indicate a more serious problem with anything, or can we ignore it?

Had this problem recently, horrible noise! Was caused by a worn-out washer (or something similarly small) which was easily replaced. So not the pipes at all.

Do you have a loo or tap anywhere that constantly runs? We had this previously and if we ran the tap it made the sound stop. No idea what the cause was as we were renting and moved out before they sent out anyone to investigate!

Our en-suite toilet was making a similar noise for a while - initially I thought it was due to low water pressure but a quick look online diagnosed the problem as a worn washer as ChubbyBroccoli suggests.

This video shows you what to do and has links to what you need to buy. Only cost a few £s.

We have the same issue. We have five bathroom/cloakrooms so it took a while to locate but it seems to be an issue inside one of the showers so we are getting that replaced.

I've had this in two different properties and managed to fix it both times myself for less than a tenner on parts, and an adjustable wrench.

As others have said it was essentially a washer on the ball valve that had gone both times.

Thanks all, I'll try the washer solution.

Sounds like you might have a "water hammer"

Agree that it’s probably the rubber washer in the flush assembly. Can easily be replaced on its own, but at the most you’re looking at a new flush assembly, which is not that big a deal.