Joining waste pipe to caste iron soil stack (brass thread)

25 Nov 2010
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United Kingdom
Hi All,

I need to join a 32mm waste pipe from a washbasin to a threaded connection on an old cast iron soil stack. The connection on the stack has a brass 1 1/4" male thread.

The original waste pipe was stolen (I presume it was copper or lead) and all that is left is the brass threaded connection. The original compression nut was stolen along with the pipe.

I purchased what I thought was the correct fitting - a plastic 1 1/4" 'iron coupling' with a female BSP thread on one end and a compression fitting at the other.

When attempting to screw the new plastic fitting onto the threaded brass connection on the stack it seems that the thread is not BSP but a slightly 'tighter' thread.

So, the fitting I bought will not fit.

Any suggestions - especially where I could buy a fitting which will connect to the stack (or even what such a fitting would be called), or maybe an alternative method of jointing? :D
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Just cut the brass out of the cast iron collar which will be jointed in with lead.
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the plastic threads will be bigger that the brass ones because of strength requirements on the joint
A BSP thread is exaclly the same no matter what the material, brass, steel, UPVC, ABS. The thread is almost certainly not BSP.
Maybe spectral cav has vanished into thin air ;)

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