Expansion vessel still functions with leaking diaphragm.

JohnArnoldBrown · 2 Oct 2014

My combi boiler started losing pressure rather too frequently, and I suspected the expansion vessel. When I depressed the valve pin, no water came out, but there was that distinctive smell of radiator water/Fernox(I know not which, but the same smell I get when flushing the mag filter).
I re-pressurized the vessel with a car tyre pump, and the pressure has been constant now for a week. My question is this: Given that I have seen advice given in this forum to partially drain a radiator to act as a stop-gap expansion vessel, and given that my the expansion tank is the highest point of the entire CH circuit, could it be that, although I have a leaking diaphragm, the expansion vessel continues to do its job?

ScottishGasMan · 2 Oct 2014

You might not have a leaking diaghram. Given that you depressurised it and nothing came out, and that you filled it back up and it still has correct pressure.

Smell is not a criteria for diagnosing an expansion vessell.

Just leave it and see how long it lasts. If you find it flat in a week or two then it may need a new one, (always check the "bike trye valve" on the vessell with a little soapy water after its filled to ensure no air leak from the valve core.

ScottishGasMan · 2 Oct 2014

I am here making the assumption that you opened a drain valve on the CH system when you filled vessel? you cant accuratley pump one up and test its operation if theres no where for the water in the vessel to pump out to

JohnArnoldBrown · 2 Oct 2014

ScottishGasMan said:
You might not have a leaking diaghram. Given that you depressurised it and nothing came out, and that you filled it back up and it still has correct pressure.

>>>I only slightly de-pressurised it.

Smell is not a criteria for diagnosing an expansion vessell.

>>>Really? So why did the air that came out smell like that?

Just leave it and see how long it lasts.

>>>The problem with that is that I have to take a free standing shelf and four hundred towels/pillows/duvets out of the cupboard to get sufficent access.

If you find it flat in a week or two then it may need a new one, (always check the "bike trye valve" on the vessell with a little soapy water after its filled to ensure no air leak from the valve core.

JohnArnoldBrown · 2 Oct 2014

ScottishGasMan said:
I am here making the assumption that you opened a drain valve on the CH system when you filled vessel? you cant accuratley pump one up and test its operation if theres no where for the water in the vessel to pump out to

Yes, I understand that, but thanks for pointing it out anyway.

andytw · 2 Oct 2014

I usually put a new valve in there anyway. Halfords.

andytw

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Expansion vessel still functions with leaking diaphragm.

JohnArnoldBrown

ScottishGasMan

ScottishGasMan

JohnArnoldBrown

JohnArnoldBrown

andytw

DIYnot Local

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