Hi,
Yesterday my gf''s boiler had a low pressure light appear on the boiler (we'd been bleeding radiators), she put more water into the system using the mains inlet (think thats what its called). Now there is too much pressure - hovers around 3 (almost on red). Whats the best way to release the excess pressure? Bleed water from a radiator? And if so how much?
Many thanks
Ben
There's usually a spring-loaded knob you can turn to release the excess pressure - this will be connected to a pipe which leads out to the outside - follow that pipe back and find the knob.
Bleeding water from a radiator will do it - probably a couple of litres or so.
Do it when the system is cold, and let water out until the pressure is about
1 Bar. If you let too much out, top it up again with the filling loop - but take it steady, watching the gauge all the time.
If you open this pressure relief valve, you can end up with a small piece of debris left on the seat, causing it to continue leaking. A drain valve would probably be a better bet. Note that the pressure will be higher anyway when the system is hot.
What problems could excessive pressure cause? Is it critical?
When the system heats up the pressure will rise futher. This may cause the safety release valve to vent. As Andrew mentioned above, these can give problems once they have operated if they fail to seal again correctly. There is also greater risk of failures in pipes, valves, joints and radiators elsewhere in the system, although to be fair if a rad did spring a leak it was probably near to the end of its life anyway.
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