"Dave" wrote in message
...
My rising main is black alkathene (I think), the outside diameter is
close to 21.5mm - how can I find out what the bore is without removing
the fittings?

--
Dave S
(The return email address is a dummy)
Hi,

I have an extremely similar rising main to this. Black plastic, very close
to 21.5mm diameter.

If it's the same as mine then it's what they used to call "half inch" which
presumably must relate to the INSIDE diameter. I had a long but in the end
embarrasing heated discussion about this with the chap in the local Plumb
Center (sic) and in the end it turned out that he did in fact know what he
was talking about.

I wanted to replace the old stopcock (rather restrictive one with 15mm
copper out) with a 22mm one.

I used a "Talbot" brand push fit coupler, available from Plumb Centre. One
of the ones they do is a "reducer" adaptor which takes the following:

At one end:

Modern blue plastic 20mm (O/D) pipe OR old fashioned black "1/2 inch"
plastic pipe (they supply the correct hard plastic ring and O ring to suit
one or the other of these.

At the other end:

Modern blue plastic 25mm pipe OR probably some old fashined imperial of a
similar size.

You can see info on the Talbot range at
http://www.tycowaterworks.com/talbot/index.php

I see they appear to have been taken over by Tyco now.

I've used this to convert from the black "1/2 inch" to 25mm blue plastic
(only a few inches of this). And then I've put a big stopcock on the end of
this (again a Talbot pushfit part) and that has a 22mm copper output. Then
all my new mains pipework to the big combi boiler, showers, etc. etc is done
in 22mm copper.

It made a big difference to the flowrate compared to the old rubbish 1/2" to
50mm stopcock and all 15mm internal mains pipework.

The icing on the cake would be to replace the black plastic with modern 25mm
blue plastic all the way from the main, but that's a project for another
year.

Regards,
Simon.