New guidance issued on plastic pipes for brownfield sites

The BPF Pipes Group has issued guidance on the use of plastic pipes in brownfield sites to support drainage designers and housing developers.

Plastic drain and sewer pipes and inspection chambers have been widely used in construction for many years in the UK and are suitable for all greenfield, as well as most brownfield, sites.

Plastic pipes can be used for previously developed sites where the appropriate remediation measures have been taken to protect human health from direct contact with the soil and to protect the quality of wastewater entering the drainage system.

The guidance includes a flow diagram, setting out the steps needed to consider the effect of contaminants on ingress to drains and sewers.In the UK, 184,000 new homes were built in 2016/2017. Currently it is estimated that over 70 per cent of new housing is built on brownfield sites and this is set to increase.

A second flow diagram guides the reader in the selection of pipe material. Plastic pipes for drains and sewers are manufactured from unplasticised polyvinylchloride (PVC-U), polypropylene (PP) and polyethylene (PE).

These materials are naturally resistant to inorganic compounds such as acids, alkalis, sulphides, chlorides, sulphates and cyanide. Their properties are not affected by the presence of metals in the soil.

Where organic compounds are present in the soil, guidance is given on the type and level of contaminants which could affect the use of plastic pipes for drains and sewers.

Even where high levels of organic contamination are a legacy of the former site use, amendment of the remediation plan before work commences to remove the source of the contaminant or the pathway to the pipework may often allow plastics pipes to continue as the material of choice.

The provision of clear guidance to help those developing brownfield sites means asset owners can be reassured that waste water systems on such sites can be correctly installed first time.