The curious case of the 20mm pipework

25 Jun 2016
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United Kingdom
Ladies and Gents,

My house, it seems, is slightly non-standard. I need to replace the float valve in my cold water storage tank, but of course it doesn't seem to have a standard 15mm fitting. I believe it to be 20mm, like the mains water stopcock fitting, which is "actually" a thread diameter of about 28mm.

1. Does this sound right? The house was refurbished in about 1990.
2. Any ideas where I can get a float valve that will fit - or do I need a reducing adapter?

Your help much appreciated, as always.
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photo please.

Is it attached to a 15mm copper pipe?

I expect you need one of these (this is the best one).

Hi John,

Thanks for the really quick reply.

Yes, it is attached to a 15mm copper pipe. I hadn't realised that the first section is going to be replaced too so it looks like a simpler replacement than I thought. Here's the photo...

All the best,


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there is a fair chance you can leave the old stem in place and change it at the big brass nut.
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John, thanks. I'll keep my fingers crossed for that.

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