John Stumbles wrote:
On Tue, 06 Jun 2006 21:56:26 +0100, David Hansen wrote:

On 6 Jun 2006 13:07:41 -0700 someone who may be "Pablo"
wrote this:-

Much appreciated. I turned the hot water on and watched the tank to see
what happened. There was a continuous steady flow of hot water from the
vent pipe into the expansion tank. It showed no sign of stopping. Very
disconcerting. I have now shut the system down pending a plumber
visiting on Wednesday. I had a new pump fitted two months ago. Perhaps
they set it too quick.

Can the pump speed be reduced? Normally there is a switch on the
pump.

Yes but as I said in my reply to the original post this is only a
workaround. The system needs the geometry of the pipework correcting or
possibly converting to a sealed system. This is only possible for boilers
with an integral overheat cutout. This would probably cost in the
region of £200. [Ducks barrage of 'my mate would do it for 50p' posts]

BTW to the original poster ('Pablo'), please follow up your posts by
replying to a post in the original thread you started rather than starting
a new thread. That way all correspondence on the subject stays grouped
together.

The pump setting has been turned down and water is no longer entering
the expansion tank via the venting pipe. The plumber told me that this
piping was too small at 15mm diam and it should be 22mm diameter. He
recommended having the piping corrected. I'm going to keep an eye on
the system with a possible view to having it power flushed in due
course. The plumber said he preferred sealed system but felt that it
was not necessary to change my system Thanks for all your help one and
all.