WORCESTER 350 COMBI EXPANSION VESSEL ALTERNATIVE NEEDED.

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Hi there,

I have a worcester 350. The expansion vessel, part number 87161425060, is obsolete and I can't find anyone with stock.

So I need to fit an external vessel fitted instead. The size is 10 litres and there are plenty to choose from. Easy enough.

However, the original expansion fitting into the 350 boiler is a push fit tube with an O-ring.

upload_2020-10-18_15-45-36.jpeg


Can anyone tell me how the entry to the boiler can be blanked off so the tank can be removed?

Or tell me if there is another expansion vessel for a worcester that fits this way, that can be used as an alternative to an external vessel?

Thanks in advance.
 
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Is the current vessel leaking or is it just the membrane that's failed? If it's just the membrane, leave the vessel in place and fit an external one.
 
Hi there, thanks.

I did think of that, but the vessel is leaking a bit through the schrader valve. Not much, but it can only get worse. All that holds back the leak is the plastic cap on the schrader. I could seal it with something, but when the diaphragm eventually lets the full system pressure into the air space, I'm worried the cap would just pop off.
 
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Ah right, thanks Alec.

But it is only a dribble, and the vessel does accept a recharge, albeit it loses it over a week or three. So my thinking was that the diaphragm isn't split, just kind of porus.

Really I know I have to replace the 350 with a modern boiler. But it's a bigger job than just a simple swap, because of the kitchen layout. So this will only be a temp' fix until spring.
 
If it's only a temporary fix until Spring, take yourself down to the local Halfords and buy a new Schraeder valve core and a removal tool. Replace the valve core and that should cure the leak, then stick an external vessel on it somewhere. The diaphragm will be split, might only be a small split, but I very much doubt that it's just porous.
 
Hi, I've got shrader valves and a key - been cycling for 50 yesrs. . But when I look into the valve on the x - vessel, there doesn't seem to be any removal notches. I'll have another look though. If you say it's posible, that'll be a big help. Thanks.
 
All that holds back the leak is the plastic cap on the schrader. I could seal it with something, but when the diaphragm eventually lets the full system pressure into the air space, I'm worried the cap would just pop off.

Get a metal valve dust cap.

ED74C36B-D1A7-4A7D-A2CD-601E6F6615E7.jpeg
 
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Yep cap is the same thread. And by coincidence I happen to have metal caps on a classic car I have. I'd forgotten. Put one on the x vessel today with a bjt of ptfe for extra sealing. Bit of soapy water now not showing any bubbles. Next job is to put an external vessel in the system.

It's a bloody shame they don't make this vessel anymore, as the boiler is as good as gold otherwise and has never shown a fault in 22 years. Consigned to a scrap heap for want of one obsolete part. But if the cap works, I will delay changing the boiler for longer.
 
Just buy a metal valve cover - done it loads of times - they have rubber seals in them and they shouldn't blow off.

th
 
If water is dripping through the schrader then so will the air when you pressurise it, so change the valve insert and pressurise properly and see if it holds
 
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Re-pressurised the x vessel, metal cap on, and pressure holding. Shrader valve is leaking a bit, but the metal cap with a bit of ptfe (belt and braces) has done the job.

Interestingly, although initially there was a little water ejected from the shrader, now only air is expelled. So even though the diaphragm must be leaking for water to come out, it must be a very small leak.

Gives me plenty of time to fit an external vessel and or swap the boiler next year for a new model.


Thanks all.
 

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