Waste pipe diameters. Internal or external?

[ray99]

Hi. Trying to get organised for the weekend with parts required to remove pedestal basin and fit a vanity unit. Can't measure internal diameters at present but external diameters are
37mm for basin waste which goes into a T
43mm from the bath to one side of the T
56mm from the T to the stack
Question is do you know what the internal diameters are likely to be? They are all solvent weld pipes if that matters.

One other thing is new basin waste measures 37.7mm internal and 41mm across the threads. What size trap do I need for that?
Thanks.

 

[Morris40]

pipe sizes you'll need to ask for are 32mm, 40mm and 50mm, as far as the trap goes just get a basin trap 32mm normally a bottle trap for a basin but some use S traps, bottle traps are normally used as it will fit in the basin pedastal but for a vanity unit you might want to use S trap as they don't block as easy, either will be fine

 

[ray99]

That's great. Thanks.

 

[TicklyT]

The nominal 32, 40 and 50 are the generally accepted metric equivalents of the 1¼", 1½" and 2" Imperial sizes. The parts are still made to match the Imperial standard, but they are now measured in millimetres.

You could quote the Imperial sizes, and end up with exactly the same parts - unless you end up being served by a spotty youth who has never even heard of an inch!

 

[Morris40]

The nominal 32, 40 and 50 are the generally accepted metric equivalents of the 1¼", 1½" and 2" Imperial sizes. The parts are still made to match the Imperial standard, but they are now measured in millimetres.

You could quote the Imperial sizes, and end up with exactly the same parts - unless you end up being served by a spotty youth who has never even heard of an inch!

true, very true