Grant oil boiler

21 Nov 2020
Reaction score
United Kingdom
Hey all
I have an issue with my Grant oil boiler losing pressure, this was happening all the time and it was traced back to a leaking pressure sensor which was leaking water all over my floor, this was replaced with a new sensor.

ever since every morning I have the low pressure light on and I have to top up the pressure to get it going again.

Does anyone have any ideas? I don’t seem to have any leaks anywhere.
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Have you taped a plastic bag over the PRV to check if its discharging.
What is system pressure when Cold /Hot.
Sorry it was the pressure relief valve that was changed.
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Ok So I still have water at the bottom of the boiler which I thought was from the previous leak but it isn’t it seems to be leaking from the top of this, no idea what this bit is though! Any ideas it does have a bar indicator on it so assume it’s to do with pressure.
Try screwing down the plug first. That should stop the leak. If you no longer lose pressure, then there is your problem. You probably have 2 or 3 of these in the boilers.
I can’t seem to screw it down it is leaking a fair bit, are they easy enough to change? My next door neighbour is a heating engineer but I’ve had him in twice already, fitting a new filling loop, and pressure relief valve as that was leaking...
Just partially drain boiler and unscrew it.
PTFE on threads of new one.
Thanks assume I won’t need to drain down if I wait until all the pressure has gone as all the water would of leaked over my floor
If you get an AAV with anon return valve adapter, you will be able to change in future with minimal leakage.

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