On Tue, 22 Mar 2005 21:46:16 +0000, Johan wrote:


Hi,

Not a regular poster, but often read this newsgroup.

I have just replaced some of my cold water plumbing, and now seem to
have a problem with the combi boiler: whenever I close a cold water tap,
the boiler sounds for a few seconds as if it is about to turn itself on.
This also happens when a toilet has been flushed, and the water flow
stops. The boiler is on the first connection to the mains water. The
mains pressure is fairly high (lead pipe from the street to the house
replaced last summer). I cannot think what I have changed that caused
the boiler to do this. I used speedfit pipe and fittings (yes, I have
read lots about those on this newsgroup; I find them very easy to use).

I was old a 'hammer arrestor' would solve my problem, but this has not
worked (the one I got is made by Sioux and on the packaging it states it
will keep the pressure below 10 bar; seems a bit high to me).

Is it possible that cold water is forced into the boiler when I close a
tap, which makes the boiler 'think' a hot tap has been opened? At what
pressure would this happen?

Any suggestions on how to fix this problem?

Many thanks in advance,

Hi,

Sounds like an airlock in the HW pipe after the boiler, the air will
expand and then compress as a cold tap is opened and closed due to
fluctuation in water pressure, making water flow momentarily in the HW
pipe and causing the boiler's flow switch to operate.

cheers,
Pete.