Pipe Stormwater PVC 150 MM 6 Metre (Foam Core)Stormwater pipe is used for drainage of excess rain and ground water. Stormwater pipe is not defined or rated by wall thickness but is rated by stiffness with a minimum SN1. 5 rating according to Australian Standard AS1260. 300mm stormwater has an approximate wall thickness of 4 5 mm whilst 375 mm stormwater has an approximate wall thickness of 5 6 mm rated to SN1. 5