On 27/11/2016 15:37, mechanic wrote:
On Sun, 27 Nov 2016 13:58:38 +0000, John Rumm wrote:

On 27/11/2016 13:15, MrCheerful wrote:
On 27/11/2016 12:56, mechanic wrote:
We have a problem with pressure loss in our central heating system.
Topping up each day and loosing 1bar or so in a matter of hours
shows something is wrong. Brit. Gas have said there must be a leak
and they've got to the stage of suggesting taking up flooring to
inspect pipes and junctions. This is getting expensive and
disruptive! BG have a £1000 limit on their part of repair and making
good costs. Have people tried:

http://www.adileakdetection.co.uk/le...tion-services/
http://www.leakdetectionspecialists....erty-leaks.htm
http://www.leakbusters.net/
(There are others)

Any experience with one of these companies? Pin-pointing the leak
position may save money in the long term, even though the survey
will cost a few hundred pounds. I've yet to explore the home
insurance angle to reclaim some costs.


Can you isolate sections by adding ball valves, then you could narrow
down the likely fault area.
But first off have you checked the obvious stuff like the pressure
relief valve (which can and do leak after a time) Air bleed valve
(mine is a brass pot on the pump) Pressure in the pressure vessel (if
this has no air pressure then system pressure can go high and lose water
through the pressure relief valve)

Yup this...

If you tie a sandwich bag (or similar) over the end of the pressure
relief pipe outside with a rubber band, you will be able to see if any
water is being discharged though that over the day.

Yes, actually I had a bag over the condensate pipe all day today
(with the boiler off) to check for leakage via that - nothing. The
PSV was replaced last week when this problem first surfaced, and the
washers and seating were perfectly dry. There must be considerable
water being lost somewhere but no sign of it on the surface, around
rads, hot water cylinder or boiler. The BG guy is coming next week
to blank off the pipework in order to separate the boiler from the
rad feed pipework. Not sure which is the most expensive outcome as
apparently the boiler is now too old to have full parts support.


The pressure relief pipe would be the most likely, if your loss is from
the condensate pipe then the boiler heat exchanger has gone, in which
case it is probably time for a new boiler.