Unions are a common fitting found in plastic pipe systems. Used either as a stand alone fitting to enable the separation of a pipe system for maintenance or repair, or as part of a valve assembly, they simplify the construction and management of pipe systems. There is however a problem here. The bodies who set the specifications for PVC and ABS pipe systems such as British Standards (BS), American Society for Testing and Materials (ASTM) etc., provide standards for pressure and quality but do not provide any standard threads for union connections. The result of this is that many manufacturers produce unions as single fittings, and on valves, that are not compatible with other manufacturers.

At Plastic Pipe Shop, our aim is to supply a “specification” rather than a make. The advantage of this approach, especially in this economic climate where companies are under pressure from the accountants, to hold less and less stock, means that we can source compatible fittings from as variety of manufacturers, all of whom meet certain criteria (BS, ASTM, ISO9001 etc.) and be sure that the customer gets the parts when they need them. Through investigations we have found that the following manufacturers are cross compatible:

Union fittings: ERA, Comer, Effast & Cepex are cross compatible. Spears, Durapipe and George Fisher are not compatible with any other makes.

Valves: Comer, Effast and Cepex are compatible although there is a couple of millimeters difference in the length of the valve bodies, which shouldn’t cause any issues unless the plastic pipe system is very tightly installed. No other valve unions are cross compatible with any other make. Other manufacturers valves are not compatible with any others.

It would be nice to think that in the coming years, as new moulds are manufactured, that the world’s plastic pipe companies could get together and form a consensus on e standard union thread, and standard valve dimensions. Whereas I an see that some manufacturers like to tie people in to their product once they have used it, life would be SO much easier for fitters and suppliers if these things were standardized.