On 26/04/2018 19:56, Tim+ wrote:
Nightjar Wrote in message:
On 26/04/2018 17:25, Jim K wrote:
Anyone know the i.d. of 50mm plastic waste pipe?

50mm *is* the ID. The OD will be 54mm if you have push fit pipe or 56mm
for solvent weld pipe.


That's confusing. I thought the convention was that "pipe" is
sized according to its external dimension (hence compatibility
between 15mm pipe of different materials) whilst "tube" was done
on internal diameter.

Have I misunderstood or is the convention not really a convention?

Traditionally, plumbing was always sized by the bore in inches. It was a
lot easier to calculate flow rates that way. That has changed over the
years, but not in a consistent way. Steel and plastic pressure pipe is
still sized by its bore in inches. Metric copper tube is sized by its OD
in millimetres, although Imperial copper tube had been sized by its bore
in inches. White plastic waste pipe is sized by its bore in millimetres,
while other drainage products are sized by their OD in millimetres.


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Colin Bignell