Key standards for Hot and Cold Water Systems
BS Standards
7291	Thermoplastics pipes and associated fittings for hot and cold water for domestic purposes and heating installations in buildings. BS 7291: 2001 is the UK product standard for plastics pipe and fittings for hot and cold water and heating.   The UK has adopted higher service and malfunction temperatures for thermoplastics (i.e.  polybutylene and cross linked polyethylene) than those prevalent in Continental Europe, with the highest classification being Class S. Third party certification to this standard signifies full compliance with the WRAS water quality requirements. .
BS EN ISO Standards
15875	Plastics piping systems for hot and cold water installations - Cross linked polyethylene (PE-X). Please note that this standard does not cover all applications for the UK. Specifically it excludes Class S.
15876	Plastics piping systems for hot and cold water installations - polybutylene (PB). Please note that this standard does not cover all applications for the UK. Specifically it excludes Class S.