Replace Imperial radiator with shorter metric - what fitting?

9 Jan 2017
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United Kingdom
How do I connect a 15mm pipe to a 1" diameter male "O" ring type fitting?

See photo.

I am replacing an Imperial radiator in a single pipe system with a metric one which is quite a bit shorter. I have bought a 1/2" Danfoss Randall RA-G Single Pipe TRV Body which comes with a chrome fitting which screws onto the 1" diameter outlet of the TRV and screws into the radiator. Job done ... or it would be if the radiator wasn't 60mm away from the TRV body! (see I searched the forum and while there are other similar posts they did not seem to address this situation.

I need to bridge the 60mm gap between the TRV male thread and the radiator at the flow end (or the same size screw fitting at the other end of the radiator). I have bought the Radiator Extender Tails shown which, when screwed into the radiator, present a 15mm pipe to the TRV valve body.

How do I connect these together?

Or am I best to use a pair of obtuse 15mm offsets so that I can move the vertical pipes closer to the radiator by zig-zagging them across?

In a triumph of hope over experience I thought this would be a common problem and an off-the-shelf adapter would be available which is telescopic, and which has a 1" female nut on the "left" end, and a standard radiator male thread on the "right" end.

Any assistance will be gratefully received.

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Thank you for replying. Unfortunately I cannot see how to use it to do what I need but their catalogue has Perfect Pump Valves 22mm at which looks to be what I need if I ignore the valve :) as it looks like it has a 1" O-ring/seal screw fitting on the "left" and a 15mm compression on the "right".

I will pop into Plumbworld and see what they suggest - I could not find anything by searching them or Screwfix.

I hope to do it centrally as I need the same arrangement at each end ... I am hoping I have space to fit both in.
Forgot to add the image. I would like one without the tap!
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I cannot see how to use it to do what I need

Surely you fit your valve, then the tail that came with the valve (dead center of your photo), then the tail extension that I linked to, then the radiator. At what point does that not connect up?
Sorry - I do apologise. :oops: You are quite correct!

I did not spot that the extender you pointed to has an internal thread and it was only your "TRV > tail came with it > tail extension you linked to > radiator" comment which allowed me to see how it worked. The picture had it the wrong way round for my use so that threw me too - obviously a barely lukewarm IQ here! Before you ask, I don't sort nails into those with their head on the left end and those with their head on the right end!

It therefore works like in the image below where I can cut it to the length I want. I will have to guess the length (I don't know exactly how far in the thread will screw) but the up-pipe will flex enough to cope with it. It will look a lot better than the one with the tap handle :)


As a matter of interest, they sell the extender tails I pictured above. How on earth does one use them as they seem to need an adapter of the type in the edited photo below.
valve 3.jpg
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Don't cut to length; you can buy them in various different sizes, in 5 or 10mm increments.

The adjustable tails that you havw are designed to fIt directly to the valve, but your valve has the wrong thread.
I guess my TRV design goes back to the 1950s as it is a specific single pipe system valve.

I was trying to chuck away the adapter which came with the TRV whereas I should have been looking for an adapter which screwed on to the adapter which came with the TRV.
Plumbcentre has few options but there are lots of options on eBay where you can also buy the extenders above for twice what Screwfix charges. See

Toolstation you pointed me to is excellent. They carry the entire range so you can mix and match to go up in 5mm increments. I bought two of each on a sale or return basis - I have 30 days to take them back. It's just as well I did - I couldn't use the lengths I had thought I needed.
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