Brighton Reticulation

Running Conduit for Pipe and Wire – Size Matters

If you are running some conduit for future pipe and wire then the size of the pipe is crucial and knowing what type of pipe you are laying is also critical.

Did you know that retic pipe is measured by the internal diameter whereas electrical conduit is measured by the external diameter?

This makes a huge difference if you are using it as conduit. Recently I was working on a job where the owner told me she had run 40ml conduit all the way from front to back. This sounded great, but when I arrived I discovered it was actually electrical conduit… not so good after all…

You see I needed to run a 25ml mainline retic pipe as well as a length of 5 core wire through that conduit.

So let’s assume the retic pipe is 25ml internally plus the width of the pvc which makes it approx 28ml on the outside. Then add 7-8ml of wire. The electrical conduit is 40ml externally, but only 36 or 37ml internally. This sounds like it will just fit BUT… over a span of 20 metres there needs to be joins in the pvc and the flared end of the pipe is approx 35ml in diameter, so it wouldn’t work.

We finished up having to run 20ml PVC and fortunately it was only a small area that required reticulating so it didn’t present a problem.

However the lesson is – if you are going to use conduit then make sure it can fit the flared end of the 25ml plus wire, otherwise you will be disappointed!

For help with any of these issues call Andrew on 0400044236 or email



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