Don’t let disaster strike head!
Barrier pipes play a crucial role in preventing contamination of drinking water. But the growing number of product options can cause pitfalls for unwary installers, Richard Graty says.
Barrier pipe systems are commonplace in brownfield redevelopment, securing water supplies against infiltration by any chemicals still present in the ground. They also offer protection against future contamination of drinking water by surface run-off, as a result of accidental spills and from locations such as petrol station forecourts.
As industrial land reuse has increased so too has the number of barrier pipe solutions in use in the UK. When working on brownfield sites, plastic barrier pipes are now predominant in contaminated land applications, particularly in the smaller diameters.
Manufacturers have introduced purpose-designed plastic pipes and fittings with an integral barrier component. Some also offer complete PE pipe systems that are fully approved by the water industry for use in contaminated land.
The growing number of product options for piping water through contaminated land has introduced a serious pitfall for unwary installers – if they assume that products are interchangeable. While manufacturers size their pipes and fittings according to industry norms, pipe systems are not standardised.
It is inadvisable to expect that a fitting from manufacturer A can be used with any success on pipe produced by manufacturer B unless the combination is specified in the product information.
The Water Industry Standard (WIS) relating to polyethylene barrier pipe systems for potable water in contaminated land is WIS 4-32-19, which defines performance characteristics and specifies contaminant protection limits for the pressure pipe and compatible fittings. Unless a specific combination of pipes and fittings has been tested successfully, it can never be approved to WIS 4-32-19 and may not be suitable, indeed even fit for purpose.
The standard was introduced in 2008 and any confusion regarding WIS 4-32-19 still remains to be clarified. Recently, a pipe manufacturer incorrectly asserted: “To be effective and meet the new UK standard it is desirable to use metal fittings, as plastic fittings do not provide the barrier properties for the total system, and thus such systems fail to meet the requirements of the standard.”
On the contrary, systems incorporating plastic fittings can and do meet the standard requirements. Protecta-Line – one of the first PE barrier pipe systems to be introduced to the UK – was among the first to get WIS 4-32-19 approval by obtaining a BSI Kitemark for the whole system.
Crucially the emphasis in gaining approval lies with the system, not individual parts. For a system to achieve WIS 4-32-19 approval, each variation of the system must pass the appropriate testing. The fittings and joints must be tested and approved in combination.
When alternative fittings have not been approved, the consequences can be disastrous. Water companies and contractors must be aware that there is a clear risk of practical difficulties and delays during installation.
Not only will the installation be affected but the performance of the installed pipes and fittings will also be in question. The result will not be WIS 4-32-19-approved, even if the core system carries the BSI Kitemark. It should be permissible to use different pipe systems on the same site. However, it is vital to terminate each system correctly before it connects to another. The correct way to do this is to terminate each system with the fitting tested and approved for this particular system.
Individual water companies are averse to allowing any contact between drinking water and aluminium, so it is important to use approved fittings that prevent such contact.
The demand for barrier pipes will continue to grow and the their use will become more familiar to contractors and water companies alike. According to figures published last year by the National Land Use Database the total area of previously developed land in England alone is at least 62,000 hectares, and the majority will be redeveloped to provide housing with a requirement for buried water supply lines.
A significant proportion of these supply lines will be installed in PE barrier pipe, as it offers the same benefits as normal polyethylene systems, in terms of ease and speed of installation, longevity and sustainability.
With the potential for water contamination at stake, it is crucial that such barrier systems are not compromised by the use of unauthorised, alternative fittings.
Richard Graty is marketing manager at GPS PE Pipe Systems. W: www.gpsuk.com
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