gas bolier water pressure

strandsman

what should the water pressure be reading on the gas boiler, it was reading zero so i turned on the tap under the sink (not the mains stop cock) and the pressure rose up but then it seems if the water was constantly flowing through so when i turned off the tap again the pressure backed off to near zero again.

DGOBS

Look outside to see if the safety valve is leaking (pipe outside behind the boiler)

If not, you have a leak somewhere else

strandsman

ya was thinking it might be somthing like that but looking outside could not find any water escaping, from any part of the building, where typically would the valve be located?

heinbloed

....where typically would the valve be located?

The valve would be located at the expansion tank, but it's outlet somewhere outside at the roof. Provided you have on open/vented CH system.
This outlet pipe could be very short and ending in the rain drain/-gutter, so it might be invisibel from the garden.

DGOBS

sounds more like a sealed system, as OP said they increased water pressure with valve under the sink (assume a filling valve)

the pipe should be on the outside wall where your boiler is mounted on the other side

strandsman

cant find the outlet, plumber time i'd say!!

strandsman

Just to close out the OP. The safety valve was leaking hence the loss of pressure, Also found the pipe that takes the released water and it was not piped to a out flow it was just left hanging behind the kitchen units and left to dribble on to the floor!!!!Anyway it's sorted now.