Low Pressure


Postby Low Pressure » Wed Dec 17, 2008 9:45 pm

Does anyone know a way of testing the central heating system to see if there is a leak?

Before I go tearing the house apart, I'd like to confirm that is the cause of my low pressure in my gas boiler. I feel it might be the diaphram in the boiler itself.

It can be expensive to hire someone to try and find out.

Thank you.
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Postby plumbbob » Thu Dec 18, 2008 7:26 pm

Many boilers have isolation service valves installed on the underside where the heating pipework connects to the boiler fittings. These may only be seen as screwdriver slots in the elbows but allow the boiler to be isolated from the heating circuit.

With the boiler off, turn them off and wait for the pressure to drop. This will take a fair while. Also, by opening a bleed valve in an upstairs rad, you can see how long it takes the pressure to be lost in the heating circuit. Because there isn't an expansion vessel on the circuit any leak will result in lost pressure very quickly. If it is a bad leak 20 - 30 mins is enough to lose all pressure so nothing will squirt out of a bleed valve.
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Postby htg engineer » Thu Dec 18, 2008 8:55 pm

If you keep losing your system pressure - then it's very likely there's a leak.

What diaphragm ? does the pressure rise (alot) when the boiler is in use ? if yes then it may be the expansion vessel at fault.

htg
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Postby Low Pressure » Fri Dec 19, 2008 12:50 am

The pressure can rise quite a bot at times when the boiler is in use, it can raise by almost 1 Bar
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Postby Low Pressure » Fri Dec 19, 2008 12:51 am

[quote="htg engineer"]If you keep losing your system pressure - then it's very likely there's a leak.

What diaphragm ? does the pressure rise (alot) when the boiler is in use ? if yes then it may be the expansion vessel at fault.

htg[/quote]

Yes, it can riase almost 1 bar when in use
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