In an earlier contribution to this discussion,
Richard wrote:

Friend is removing one rad and replacing it with two others. In
lifting the floor he has found that the main supply around the first
floor is in thin wall steel pipe with what appears to be 15 mm copper
tee-ed off to the actual rads. I've measured an offcut of the steel
as being 21.5 mm OD with walls of about 2.5 mm.

WTF????

The offcut is showing only very faint signs of rusting the (hacksaw)
cut end. The pipe can be cut without difficulty with an ordinary pipe
cutter. It is not, according to my magnet, stainless steel - is that
a reliable test?

He's a little perplexed as to how he inserts new tees to supply the
new rads. Slipping a 22 mm end feed joint onto the offcut reveals a
large gap that I think is too big for soldering.


Q: What is the steel pipe? What fittings should/can he use? Is all
lost!

TIA

Richard

As others have said, so-called stainless steel pipe was used in the 60's and
70's when there was a copper shortage. The sizes will be 1/2" Imperial**
(virtually identical to 15mm) and 3/4" Imperial - whose OD is just slightly
less than 22mm. You can use 15mm compression fittings on the 1/2" stuff, and
22mm compression fittings with special imperial olives on the 3/4" stuff. I
wouldn't advise trying to use solder fittings on this pipe.

** Imperial pipe sizes refer to the nominal ID rather than the OD - which is
why 1/2" pipe is actually more than 1/2" in diameter - and the same for 3/4"
--
Cheers,
Set Square
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