/diy/ - Do It Yourself

>>1722681
>if they say 25mm, it is 25 OD
PVC pipes follow NPS dimension standards, meaning that up to 12", the inside diameter of schedule 40 pipe is pretty close to the nominal size, with different schedules having different inside diameters. 14" and above, the nominal size is the outside diameter.

>>1722722
>Isn't nominal pipe size supposed to be somewhere between ID and OD?
No. It's based on historical use practices based on needs for pressure rating and flow. The nominal pipe dimension in modern sizing practices is close to the traditional internal diameter of "standard weight" iron pipes of that nominal size. Other pipe weights of the same nominal size vary the internal diameter so that they can use the same fittings as other schedules. "Standard weight" corresponds to the modern schedule 40. Higher schedules have a smaller-than-nominal internal diameter, while lower schedules have a larger-than-nominal internal diameter. Copper pipe uses a different system due to its historically different uses. See pic.

>>1722777
1/2" is precisely 12.7mm