In short
Sizes of solvent cement jointed pipe & fittings, less than 8”NB commonly sold in Australia, are generally to one of the following international standards AS 1477, ASTM D 1785, BS 4346. These systems have the concept of nominal bore “NB”, this is known as the imperial system to differentiate it from the metric system. In the USA the term IPS means iron pipe sizes but this is also an imperial system & uses the same principle as the Australian & british standards.
In the imperial system the outside diameter is fixed & the wall thickness varies depending on the pressure rating of the pipe. Hence though a pipe may be sized as 2”NB, neither the inside or outside diameter need be exactly 2”. In Australia, because we are a metric country using an imperial PVC pipe system, it is common to specify pipe by the metric equivalent of the NB size. For example: 2” NB is sold as 50mm pipe but the actual OD (outside diameter) is 60.3mm & the actual ID (internal diameter) of shed 80 is 48.5mm. In the metric system “NB” is denoted as “DN” & “OD” is denoted as “d”. The convention used by Merriman is to offer imperial pipe sized on NB quoted in inches e.g. 2”NB, or the metric equivalent of the NB size e.g. DN50. If the product offered is a true metric size we offer sizing on “d” in mm e.g. d63.
In the true metric system, DIN 8062, the pipe is sized on the actual outside diameter, so in the case of d63/DN50 pipe, the measurement of the OD will be 63mm.
As we operate in a world of global trade it is increasingly common for equipment to be imported into Australia from europe & china who predominately manufacture pipe & fittings to the metric standard DIN8062.
If doubt exists as to which standard an installation complies, use the table below, or advise us the actual outside diameter of the pipe, to determine if it is an imperial or metric pipe system.
The following table compares actual dimensions of the outside diameter of metric & imperial pipe. In most sizes, the imperial systems (Australian, british or american standards) are interchangeable. The exception being 2.1/2″NB.
In most cases metric & imperial sizes are not interchangeable. The exception (not recommended) being 3″NB/d90 subject to the tolerances of the pipe & fittings & the use of an approved Spears® schedule 80 gap filling solvent cement.
- Important information on PVC pipe sizes & international standards
- It is vital to understand in most sizes, metric fittings will not fit imperial pipe & visa versa
- Hence we offer a range of metric to imperial adaptors to interface the two systems
