Expansion Vessel Replacement

[Rory]

Hello

Our boiler (Baxi 100 Bahama) has been playing up lately (hot water not kicking in, heating not working). We discovered the system pressure had dropped to 0 a while back so we repressurised it to 1.5, pressed reset and got our heating back... temporarily. We have had to repressure the system at least once a day for the last 2 months. I assumed it was a leak but could find no evidence of this, and a friend suggested a fault on the pressure release system might be to blame. I found a pipe that goes out the back of the boiler to the outside of the house, and it does drip, so assume the pressure is escaping there.
Having searched the forums here I saw a thread about a similar problem which gave details on how to check if the expansion vessel is faulty. I think I have found mine (took cover off boiler, flatish red metal chamber located above control panel). I pushed the pin in the schraeder valve and water comes out... I take it this means the vessel is knackered?
Though I'm not a heating engineer I'm happy to replace this myself if it will solve our problems and there are no gas connections involved. What's the procedure and would I need any specialised tools? I have seen replacement vessels online for around £50 ex vat, is there anywhere cheaper online or around Bristol?

Many thanks in advance

Rory

 

[weargas]

I take it this means the vessel is knackered?

yes, yes it does.

replacement is as easy as falling off a frog;
1. switch off the electricity supply to the boiler
2.decide whether to drain just the boiler or the whole system. If you drain just the boiler you may risk the service valve starting to weep if you switch them off. A better way is to drain the whole system only for the fact that whilst it is drained you can introduce a fresh dose of inhibitor.
3. remove the casing from the boiler and have a few rags and a dish ready underneath the boiler as complete draining of the boiler won't have occured (there's always a little left in)
4. on the left hand side and underneath the expansion vessel is the single and only connection to the vessel. undo it slowly and wait for the remaining water to drain from it (if you want to do it the heating engineer way attach a pump to the valve and pump the water out after the system has drained)
5. when there is no water left and the connection can be broken without losing water everywhere undo the nut. the vessel is clamped in place by 2 bolts. loosen these and the vessel should just ease forwards and out.
6. clean the flange face on the pipe that connects to the expansion vessel, removing any of the old sealing washer. you might want to check whether a new washer is supplied with the new vessel incase you need to salvage the old one. A new one is always better though
7. it could be worth dismantling the prv and cleaning any dirt from the sealing face or better still replace the prv (easier done while the system is already drained) if you're gonna put inhibitor in you don't wanna lose it through a dripping prv.
8. reassemble in reverse order. don't overtighten the connection, if it leaks you can always give it a little nip
9. get the missus to take photos of you doing it then post them on here if things go wrong...............at least you'll have entertained.

 

[Rory]

Thanks weargas, all working fine now!