How do you explain the pipe joint?
For example, a 4 point tube is 1/2 inches, and this size represents the diameter of the inner hole, that is, the passing diameter of the fluid.
The fittings are expressed in part according to the British system
Steel pipe marking should be DN, DN is nominal diameter, DN20 galvanized pipe does not mean that the outer diameter of the pipe is 20mm, the outer diameter of the steel pipe, but 26.8mm; DN15 galvanized pipe, the outer diameter is 21.3mm.
