The specification sizes of PVC water mains are φ20, φ25, φ32, φ40, φ50, φ63, φ75, φ90, φ110, φ125, φ140, φ160, φ180, φ200, φ225, φ250, φ280, φ315, φ355, φ400, etc. The pressure shown by the PVC feed pipe is expressed as nominal pressure, expressed in MPa. Nominal pressure is set at 0.63Mpa, 0.8Mpa, 1.0Mpa, 1.25Mpa, 1.6MPA and other 5 kinds. The minimum caliber tubing for each pressure zone is specified as: the smallest aperture of the 0.63MPA pipe for the 63mm,0.8mpa pipe is the least small aperture for the 50mm,1.0mpa pipe and the minimum aperture for the 40mm,1.25mpa pipe is 20mm and 25mm for the minimum calibre of the 32mm,1.6mpa pipe. Pipe length is generally 4m, 6m, can also be negotiated by both supply and demand.