Unvented cylinder leak (and maybe replacement - nooo!)

8 Dec 2008
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United Kingdom
Hi all

Firstly, thanks for reading this message and (hopefully) helping me out!

I have an unvented pressurised hot water cylinder which has started to leak.

Where from is hard to say, but it appears to be from the immersion heater points. Upon first discovering the water dribbling down the side of the cylinder, I called out a plumber who removed the upper immersion heater and pointed to where the casing was slightly covering the hole, meaning that (in theory) the washer wasnt sitting quite flush, hence the leak.

After cutting away the part of the cylinder casing covering the hole and replacing the washer on the immersion heater, the plumber advised me that the leak may still continue for a few days because the foam surrounding the inner cylinder would have absorbed a lot of the water. Its now day 3 and there is still around an ice cream tub full of water leaking out over approx a 10 hour period.

I looked again this morning and noticed a rusty trail of water not from the immersion point, but from the cut in the casing approx 1 inch away.

I think that the lower immersion point is now starting to leak, which should be fixable, but my main concern is that the cylinder is leaking from another point, hence why the water continues to seep out of the foam. Is that common / possible?

If the worst comes to the worst, and I have to replace the cylinder, please can you recommend a good replacement make, and how much (roughly) a plumber should be charging to fit it?

Many thanks


PS Current cylinder is as old as my flat (approx 13 yrs), and my flat is ground floor so mains pressure is quite high.
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Hi - no, he just cut a small bit of casing around the hole to remove the bit that was overlaping
I hope your plumber is registered to work on un-vented cylinders.

Can't give an approx price without knowing what size it is and whether it's direct or indirect.
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Put one of these in. Stainless, no annual service and can even be DIYed. Run the CH off it too having a Smart pump on the CH loop and then you can have TRVs on all rads and no electric wall thermostat. Put a Magnaclean filter on the CH return pipe to the cylinder. This is not a direct safe replacement for an unvented cylinder, as it offers so much more than an unvented cylinder, a superb CH buffer too, and costs about the same. No contest.


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