Can you just put an adaptor from where you need to extend from and then use 20mm?

https://www.edwardes.co.uk/products/lewden-pd1452a-3-4-male-x-20mm-female-conduit-adaptor-galv-steel?gad_source=1&gad_campaignid=18306676680&gbraid=0AAAAADsbJ5862Oqie7-r4uInNso4-qu6o&gclid=CjwKCAjw2rrQBhBuEiwAarLWHf2LsZtIvDUC9MClbbFHzvJmS98vlWdgXTGTQ0TX4pgF2jzLrsxFSRoCjOQQAvD_BwE

On 21 May 2026 at 15:28 Andrew Tinsley Said:

 

…..P.S. I always prefer imperial material rather than Metric if I have the choice.

Well call it 25/32″ pipe. Seriously the stuff with threads on might actually be 20mm but with 3/4 thread cut on

On 21 May 2026 at 09:33 Andrew Tinsley Said:

Bizzarely, there are no end of suppliers offering 3/4″ pipe

Would it be possible to provide links to one or two of those?

You could look up when BS 31 was withdrawn (31 August 2015). That may give you some indication of why finding a supplier is difficult.

On 12 August 2026 at 21:52 paulmichael1084 Said:

Firstly I’m glad you have got sorted out.

I wonder if the 3\4″ pipe you are seeing is BSP air pipe?

In my experience electeicians use metric sizes (M16, M20, M25 etc), whilst pipe fitters use BSP fittings and pipes, 3/8″, 1\2″, 3\4″ etc.

If anyone needs the latter then Boules in Stockport are a reliable source.

@JasonB I know the yanks still use imperial electrical conduit

Paul, at one time imperial electrical conduit was used by electricians here in the UK and that is what the OP is looking for to add to his existing old installation.

The main differences is that conduit is measured by the OD so the 3/4″ conduit is 3/4″ OD but pipe fitters would be 3/4″ bore which is just over 1″ OD the latter is what you see being used for air, gas etc., though it is giving way to the blue aluminium push fit air pipe and fittings which are sized by metric OD. Your typical 22mm OD air and plumbing copper having the same 3/4″ ID as the old threaded pipes