Worcester Bosch Boiler Pressure

[TJ1]

When the central heating is off the pressure on the Worcester Bosch boiler drops to 0. When it fires up it then goes to 1.5 which I think is correct. I tried putting more water in but it then goes to between 2 and 3. I have bled the radiators and they seem fine.

Does anyone have any idea please why the pressure keeps dropping and is it doing any harm to the boiler. Other than that it seems o.k. The boiler is 8 years old and in on a maintenance programme with British Gas.

 

[mrgas]

Your expansion vessel needs attention, and most likely your pressure relief valve will need changing.
Why not phone BG and get them to sort it