1 Scope
This part of BS 7291 specifies general requirements and methods of test for polybutylene (PB) pipe and
fitting systems intended for use within buildings for the conveyance of cold water,
including drinking water, and heated water for use in domestic hot and cold water
distribution and heating installations. These requirements supplement the general
requirements in BS 7291‑1, which are also applicable.
NOTE 1 Before reading this part, it is essential to read BS 7291‑1.
NOTE 2 Methods of test are given in Annex A, Annex B and Annex C. Annex D gives guidance on factory control procedures.
This standard specifies general requirements for materials to be used for, or in the
form, of PB monolayer, multilayer or barrier pipes, and associated fittings and components.
Particular requirements are also specified for PB pipe alone or jointed with push-fit,
fusion or compression fittings conforming to BS 7291 or other British Standards intended for use with pipes conforming to this part.
This part of BS 7291 provides for pipes dimensioned to suit two established metric series: BS ISO 4065 for thermoplastics pipes generally and BS EN 1057, for compatibility with copper pipework systems widely used for these applications.
This British Standard is applicable only to Class “S” pipes and fittings.
It does not specify dimensional requirements for fittings because the performance requirements
specified for fittings, when tested individually or in assemblies with pipe, are intended
to ensure that the dimensions of the fittings are satisfactory for jointing purposes
and pressure containment.
NOTE 3 Pipes and fittings of non-barrier PB are to some extent permeable to oxygen; hence,
if they are used for the primary circuit(s) of a heating system, it might be beneficial
to add a corrosion inhibitor to the fluids circulating therein. In such a case the
manufacturer(s) of the pipe and/or fitting should, upon request, provide advice in
accordance with BS 5955‑8. This advice should include selection of a compatible corrosion inhibitor and/or
methods for reducing the permeability.