lossing pressure ?

I assume that it keeps doing it. After you top up pressure.
You have a leak.
Depending on how quick the pressure drops, faster the drop bigger the leak. Check round all your radiators, inlet/outlet, top and bottom, use your hand, WHEN the system is cold. That way your hand will get wet, when you find a leak. If the system is hot, could evaporate the water, before you get to check. Look for signs of leak, brown staining etc, Might not be much, Could just need a little tightening of a fitting, Careful if tightening a fitting, do not allow other parts to move, cause another leak. Do not over tighten a fitting, worse than under tightening it. ( if under tightened, you can tighten it, IF over tightened, could still leak, but would need the fitting/pipe replaced to fix) or if leaking around the top sealing plug or the top bleed vent plug, (the one that you let the air out of), Plug/seal, might need replacing, quite often, just a rubber ring around the metal bit. Dont forget to make sure all the air bleed vents are fully closed.

SD
November 2011

is water coming out from pressure valve follow the out let pipe if any water mark out side boiler wall, change valve ,look out any leaking pipe in property any small water loss will drop pressure

ltd
November 2011