The first British Standard for Rubber Joint Rings for Gas Mains, Water Mains and Sewers was published in 1955 giving guidance on elastomeric material performance.
After many years of working with such national standards, in 1996 the European Standard EN681 was published “Elastomeric seals — Materials requirements for pipe joint seals used in water and drainage applications”. This document was a harmonisation of the EU national standards but also based on ISO 4633 and ISO 9631, bringing these two sets of requirements for cold and hot water respectively under one specification.
EN681 is a ‘materials’ standard giving details of the physical requirements of the elastomer material including:-
- Hardness classification
- Tensile strength
- Elongation at break
- Compression set
- Stress relaxation
- Volume change in water
- Ozone resistance
General requirements for finished joint seals are also given but any additional requirements called for by the particular application such as seal geometry, joint design and performance are specified in the relevant product standard.
Over the years natural rubber was replaced by synthetic elastomers due in part to their superior microbiological deterioration resistance. The most common elastomers used for water, drainage and sewer applications are SBR and EPDM and TPE. NBR may be used when oil resistance is required.
EN681 Part 1 Vulcanised Rubber, is currently under revision and will probably be followed by Part 2 Thermoplastic Elastomers, ensuring that the standards to which elastomeric materials for pipe joint seals used in water and drainage applications are state of the art and fit for the future.