The specification defined the requirements for construction, materials, dimensions, joints, marking, testing, workmanship, inspection and certification of Polyester Resin Concrete (PRC) segmental linings for the renovation of sewers where the lining is designed to act with the existing sewer fabric and annulus grout to form a composite structure i.e. Type I design.
The WUK Standards Board commissioned a review of WIS 4-34-05 Issue 1 that concluded in March 2023. Based on the review’s findings the Board determined that the document’s status should be changed from ‘current’ to ‘archived’ since:
- The WIS was published in 1986 and has not been revised since that time (although it was reprinted in June 2006 for web publication).
- The WIS is limited to the manufacture of pre-cast units and does not cover installation.
- The materials and product described are for practical purpose no longer used within the UK water sector.
- The WIS references 13 British Standards. Nine of these have subsequently been withdrawn – mostly because they have been replaced by later British, EN or ISO standards.
- The key materials aspects of WIS 4-34-05 have been largely superseded by BS EN 14636-1:2009 Plastics piping systems for non-pressure drainage and sewerage – Polyester resin concrete (PRC) – Part 1: Pipes and fittings with flexible joints.
- Although CESWI 7th Edition lists the WIS as a reference, no actual referral to it was identified in the body of that document.
- A list of consultees was developed by approaching sewer renovation contractors known to use pre-fabricated panel systems and others known to the reviewer, and a search for those whose advertisements in trade journals such as Drain Trader, indicated they may undertake relevant work. Very few possible candidate consultees were found. These were asked whether they knew anyone else that may have an interest in retaining the WIS.
- The resulting consultee list for the 2023 review was limited (7 individuals) reflecting the small number of active UK contractors installing pre-formed panel Type I lining systems. However if there was an active player in the UK market providing polyester resin concrete lining panels for this purpose it would be unusual for them not to have approached any of the principal contractors likely to install them in order to make them aware.
- In addition to this initial consultee list a simple questionnaire was sent to the industry group UKSTT (United Kingdom Society of Trenchless Technology) and to The Sewer Rehabilitation Contact Group. Both circulated the consultation questions to their full membership.
- No suppliers were found advertising this system during a review of adverts in the UK based trade journal ‘Drain Trader’ and no UK suppliers were known to any of the parties contacted during the review.
- An internet search was undertaken using the WIS title’s key words without success.
- The “WRc Approved” website was checked for evidence of any manufacturer having any current approval and none was found.
- There is no known UK supplier of polyester resin sewer linings although the international nature of such products means they could easily be obtained from abroad if a suitable project arose. Polyester resin pipes and renovation materials are produced in a number of other countries using standards that are appropriate there.
- With no active UK supplier and no enthusiasm for revision of the WIS from the Sewerage Rehabilitation Contact Group, it would be difficult to form a group willing to undertake its revision or to financially justify it.
- In its present form, with so many out of date reference standards for input materials and for compliance tests, the WIS is too poor to use for its intended purpose of product certification.
- No UK Water and Sewerage Company has expressed a wish to keep it (based upon absence of responses from the Water UK Sewer Renovation Group).
- The WIS includes a “Typical Certificate” and a statement on whether the supplier has “…..third party certification acceptable to WRc in respect of this specification…”.This effectively gives WRc a governance role that may no longer be appropriate. Over time the acceptance of polymer/plastic products has increased and there are other bodies who could verify compliance
The WIS was produced in an era where there was rapid development of sewer renovation techniques and a need for specifications that could be applied across a fragmented client group (much of the wastewater system was still managed on behalf of the Regional Water Authorities by relatively small local authorities who would otherwise be drafting individual specifications). It was written in a manner to facilitate third party approvals (certification) and avoid the need for individual approval by many different organizations.
At that time there were many reservations around the use of plastics in sewer applications much of it linked to concerns over quality and durability. This WIS was one of a series of IGNs and WIS which sought to address those concerns but despite this, polyester resin concrete has not become widely used in the UK.