Isar HE 30 - O-ring for expansion vessel connection on pump

4 Nov 2010
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United Kingdom
Yes, we know it's an old boiler, yes we know it's overdue for replacement, but other than this one leak it's actually working fine. And no, I'm not touching anything gas related, this is a simple water leak issue.

One of our lasses has an Isar 30, and a while ago it started leaking which was fairly easy to diagnose as where the hose from the exp. vessel connects into the pump. No problem thinks I, just pop a new O-ring in having found the old one having gone hard and split :rolleyes: OK, I guess some of you are laughing already because you already knew what I found out - it's a size that's not in any of the kits all the engineers and plumbers merchants seem to have under the counter, and I have on the shelf - even a local outfit that specialises in seals etc didn't have a thicker one. Size of the "O", no problem; thickness of the ring, problem. One of the engineers checked and told me that Ideal don't sell the O-ring, only the whole pipe.
One of the engineers said they usually just wrap a few turns of PTFE round the slot to increase the diameter so the thinner O-ring will seal - which it did for a couple of years. Now it's just starting to fail again.

I could just repeat the exercise and assume it'll last for another couple of years.

Is there a source for the right "thicker" O-ring ? Or is there another trick for this problem ?
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