pressure loss from heating system?

have you checked to see if your pressure relief valve is leaking, this will be outside (the outlet) usually a small copper pipe faced back to the wall, or it could be the expansion vessel, to check this you need to de-pressurize the system and check the vessel pressure on the schraeder valve (a car tyre pressure tester will do the job), it should be about 1 bar or 14 psi, it can be re-pressurized using a car footpump or similiar, another way to test is tie a plastic bag around the pressure relief outlet and check after the heating has been running for a day or so if the bag is full of water the pressure vessel is deflated.

tojo
September 2007