When heating goes off, system pressure drops to point where low pressure light starts to flash. When heating comes on again pressure gauge can read between 2 or 3 bar. Adding some water to the system stops light coming on for a day or two. I assume that since pressure rises again when heating is on, this isn't a simple leak problem... or is it ?

David F, December 2005

COULD VERY WELL BE AS THE WATER STILL IN YOUR HEATING SYSTEM WILL EXPAND CAUSING A GREATER PRESSURE IN YOUR HEATING SYSTEM WHEN HEATED UP FIRST CHECK AROUND ALL YOUR RADIATOR VALVES IF NO SIGNS OF A LEAK ARE PRESENT GO OUTSIDE AND THERE SHOULD BE A PIPE PROTRUDING OUT OF THE WALL BEHIND THE BOILER CHECK FOR SIGNS OF WATER IE WATER LINES DOWN WALL , MELTED SNOW, IF THERE IS YOU FIRST NEED TO REPLACE THE PRESSURE RELIEF VALVE, THIS SHOULD SORT PROBLEM IF NOT THEN YOU HAVE A PROBLEM CAUSING THE PRESSURE RELIEF TO BLOW OFF

MIKE, December 2005