What do the terms 1/2, 3/4, and DN mean?
The terms 1/2, 3/4, DN refer to nominal sizes. DN means ‘diamtre nominal’ and refers to the nominal diameter of a pipe in either metric or imperial terms. Nominal size is a numerical designation which is common to all components in a piping system other than components designated by outside diameters or thread size. The parts 1/2 and 3/4 refer to dimensions of 1/2″ (inch) and 3/4″. For example, DN1/2″ means a pipe is being referred to in imperial units and indicates a nominal diameter of 1/2″, equally so, DN15 means a pipe is being referred to in metric units and indicates a nominal diameter of 15 mm. It is more usual to refer to pipes in the metric way, i.e. DN15, but there is no reason why DN1/2″ cannot be used. Different pipe standards will state different outside diameters and wall thickness.
