I recently put my heating back on today and the pressure gage shot up to 4 in seconds. I then bled all the radiators in my house and it brought it back down to 3. I then turned the heating back on and again it shot up to 4. The water is pouring out of my overflow pipe and I have now had to turn the water off from the mains. any ideas of how I can depressurize the actual boiler

Kevin, September 2010

hi
vailant combi
high pressure when on central heating...ok on hot water only...
its a blocked filter strainer in return pipe from the system to boiler...need to drain system..clean and or fit new filter......done mine couple times works every time...will also cause rads to feel luke warm..when cleaned will be hot..

clivvee, September 2011

check the central heating pump is turning.some have caps on the ends that can be removed so you can manually rotate the pump impellor shaft.No water flow can mean instant pressure build up!

A1, September 2010