The difference between pipes and tubes is simply in the way it is sized. PVC pipe for plumbing applications and galvanized steel pipe for instance, are measured in .Free Plumbing pipe sizing, and roof gutter design programs, to Australian and International standards. Suitable for PC and mobile devices, On and offline.I used your instructions to help determine the height of my desk, determine the size of pipe to use, and to determine casters sockets. I didn’t follow your entire .Yarrow Plumbing pride ourselves as industry leaders in technology, innovation and customer service. Our team of specialist plumbers are ready to help.