A couple of months ago we had a new boiler (regular) fitted. A couple of
weeks later my wife said there was a strange noise coming from the spare
bedroom en suite, which only occurred when I was using the basin in the
bathroom. I assumed it was something to to with the HW/CH pump. The next
time it happened I checked and was most surprised to find it was the
mains cold water pipe which fed the instant-heat shower that was
vibrating. I couldn't understand how the pump could be responsible, as
it was nothing to do with cold water and at least 10m from the en-suite
pipe. It wasn't, of course, and a bit of internet searching led me to
the float valve on the cold water tank; that was indeed the cause.

So yesterday I removed and cleaned it, but it made no difference; when
the tank filled and the float valve started to cut off the supply, the
vibration started again. Today I replaced the old float valve with a new
Pegler float valve. And the vibration is even worse - now we have a
foghorn! One thing I noticed was that it was possible to cut down the
sound by flexing the side of the plastic CW tank by pushing on the valve
inlet. When I removed the old valve I noticed that the reinforcing metal
plate was mounted horizontally, and that's the position I replaced it
in. But it seems to me the tank would be stiffer with the plate mounted
vertically, so that's what I'm trying. At the moment things seem to be
better, but they may not last.

If the noise returns, I'll try partially closing the tank isolator valve
first to see if that helps, as that's the easiest thing to do. If it
doesn't, I'll try the "yoghurt pot" dampener on the float arm.

But if all those fail, I think the easiest thing is to fit a Torbeck
valve instead of the standard float valve.

--

Jeff