Expansion tank question

5 Oct 2023
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United Kingdom
I have an oil fired boiler and there is an expansion tank next to it. I regularly have to top up the pressure in the expansion tank by opening the water inlet valve but everything seems to work OK (it seems to drop regularly to about 1 bar when cold and I top it up to 1.5 bar when cold). But someone told me to check the schrader valve to see if it leaks air or water - but when I release the schrader valve nothing seems to come out (even when the pressure guage, which is attached to the relief valve and the water inlet, reads 1.5 bar) so I am wondering if there is something wrong? I have also read about recharging the air in the expansion tank but don't know whether this is something I ought to be doing (and if so how to do it)?
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You are confusing the pressure on the sealed ( water) side of of the system ,with the pressure of the charge in the expansion vessel.
If water is lost from the sealed system ,that causes the pressure drop. You need to establish where water is escaping.
And it sounds like the expansion vessel needs recharging too.
As above, you will have drain down the system until there is no pressure at the water end then remove the water end EV connection pipe, pump up the air end to 1.0 bar reconnect the pipe, refill the system and keep filling until the pressure reaches 1.5bar this will give a few litres of water reserve until the pressure falls again to 1.0bar which should last for months on end after venting all air from the system and topping up to 1.5bar don't forget to add some inhibitor.

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