On Thu, 05 Jan 2006 17:33:17 +0000, Dave wrote:

Nearly a year ago I changed the old vented system to a sealed one,
whilst also adding new rads and splitting it into zones. It all works
well BUT the pressure falls VERY slowly, probably from 1 bar to 0.7 bar
over about 6 weeks.
I can't find any dampness around the rad valves or visible joints so
have resigned myself to waiting for the leak to get worse before I can
find it. Are there any suggestions on how to find the leak, or for
anything I can add to seal the leak (probably not a good idea)?

The GlowWorm book suggests a minimum pressure of 1 bar, is this just to
stop local boiling in the heat exchanger?

Loads of background info in the Sealed CH FAQ.
I doubt the relief valve is dripping but do check.

It will be almost impossible to find a leak that small.
I suggest that you partially drain down and add some internal leak sealer.
(fernox and sentinel do versions), this should seal the tiny leak up.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html