Expansion Vessel - Baxi - Main - Potterton Top Up

Datastream · May 3, 2025

Hey folks,

So I have a Potterton, and after the water pump has gone on it I changed it and when I was looking on Youtube I noticed a video about the expansion vessel, started watching it and he mentioned that if the pressure gauage after a while starts hitting three then it's more than likely the pressure vessel, so I bought a foot pump today and fitted it to the valve and there wasn't any pressure reading on the gauge on the foot pump, so I pumped it up to 1 bar, thing is the valve is on the top of the expansion vessel and getting it off quickly is a bit of a mare and the air just escapes.

So I'd been looking at a Baxi Boiler Expansion Vessel Repair Kit, but surely the air is just going to escape when this is unscrewed from the Schrader valve on the boiler?

The guy in the video says just to unscrew it quickly but it's going to leak empty quite quickly like the foot pump does, how ever it's a bad design and the Schrader valve is on the top so you can't quickly release the foot pump.

Do you jut leave the extension connected? this would allow me to remove the foot pump connection once filled quite quickly

Any tips welcome.

WhatsApp Image 2025-05-03 at 16.34.27 (1).jpeg

ShaunCorbs · May 4, 2025

That’s why you over-pressurise it slightly eg 1.3 bar ends up being around 1.1-1.2 bar when you remove it

Also did you drain the boiler and leave an open end while re pressurising the expansion vessel

Also you should be gas safe registered as your inside the combustion chamber

Datastream · May 8, 2025

ShaunCorbs said:
That’s why you over-pressurise it slightly eg 1.3 bar ends up being around 1.1-1.2 bar when you remove it

Also did you drain the boiler and leave an open end while re pressurising the expansion vessel

Also you should be gas safe registered as your inside the combustion chamber

Thanks yes I did, all good and the bioler is working perfect after years of it jumping into the red 3 + on the pressure gauge.

And being told I need a new one from 3 or 4 people that have checked it over the years, just had it chekced and the guy from the council didn't even notice or tell me the pump was leaking, but why would he after snapping off the water tap thing and hiding it behind the paneling.

I boght this place but they still service it as I'm on a lease, however, not gas registered but it's pretty straight forward and has saved me an arm an leg.