HI, i have a potterton puma 100 combi, about 12 year old and when i switch the central heating on,after approx 20 minutes, the pressure guage reads high. then left longer , say overnight, the low pressure light comes on and boiler has shut down(pilot off) and i have to top the system up and re-light the pilot. cant see any leaks. can anyone help please ?

mike w, November 2008

may be the expansion vessel diaphragm because that wont show any leaks

Paul the plumber, November 2008

hello mark the pressure relief valve is faulty .the one inside boiler with red cap and that is connected to a 15 mm copper pipe going out side of the house the valve cost about 15 pounds .

john, November 2008

is there water coming out the prv on the outside wall

b, November 2008