My toilet has developed water hammer..

[HappyPeach]

The local water company cut my water off to put a new meter in the street outside. Ever since then my toilet on the 2nd floor has developed what I think is called 'water hammer' that starts halfway through the flush-refill. It stops if I turn the tap on. How do I cure it?

We had water hammer in the pipes leading to our shower in the top bathroom (pumped up from the hot water tank). It was noisy in and, because the Saniflo unit was also ancient and needed replacing, noisy out! I couldn't hear the radio in the adjacent bedroom when DH was showering.

I'm sorry but I don't know of a DIY fix. We got a plumber who did some pipe whispering (thankfully without having to take up all the floorboards) and who fitted a new Saniflo. Now we have silent pipes and a peaceful Saniflo, and I don't have to whack the radio up. WHat does Dr Google say?

You should have a shut-off valve on a pipe somewhere below your cistern. If it's fully open, try closing it slightly, that should reduce the flow into the cistern when you flush.

We had this, it was thumping and whining. I read somewhere to turn all the taps on full in the house. Did this and it cured it, then the row started up again, repeated it & eventually it sorted it out.

It may be a partial airlock. Try doing what @OnionBudgie suggested.

We had this on a bathroom tap and it cured by attaching a hose to the mains tap (kitchen) and forcing water back through the bath tap. There was a lot of bubbling and gurgling and it cured the problem.

1. I don't think you are able to do this with a cistern.
2. I'm not a plumber and it might be completely the wrong thing to do!

This . The cistern will probably fill a little slower , but definitely the first thing to try. Maybe the new meter/ stop tap on the street has a slightly better flow than the old one and has increased your pressure a bit ?

You can fit water hammer arrestors to the pipe leading to the toilet which acts as a valve to reduce the pressure causing the hammer. Best to deal with it though as water hammers can damage pipes.

www.screwfix.com/c/heating-plumbing/hammer-arresters/cat10420003

Does anyone know the logic behind it happening at the highest point of the house? & why the loo & not the basin?

I think it could be air accumulating at that point

Open the lid of your WC cistern and take a pic of the contents. It may be that the filling valve is worn out.