Can contaminants in the soil permeate through PE pipe?
In contaminated soils no pipe system can be considered completely resistant to permeation and the appropriate pipe material selection criteria should be used. Research undertaken in the USA has demonstrated that precautions are needed in the design of all pipe systems buried in heavily contaminated soils to prevent permeation of substances into drinking water.
Many water companies have their own systems for classifying soils and Codes of Practice covering what types of pipe system may be installed. Under normal soil conditions the use of PE pipes has proven to be totally satisfactory.
Cast iron, steel and GRP systems are jointed using spigot and socket systems with natural or synthetic rubber gaskets. These gaskets are the weakest element and may allow substances to enter the water supply. In addition in the longer term cast iron and steel systems may corrode and crack providing additional paths for the ingress of contaminants.
PE pipe systems on the other hand normally use no jointing gasket as they are fusion welded and they are tough and have good resistance to corrosion. In addition PE is very resistant to attack by chemicals and hydrocarbon fuels - hence its use for petrol tanks and other containers. PE pipes can be affected by some soil contaminants, for example organic solvents. Where the pipe is to be laid through an area of known soil contamination it is recommended that a soil analysis is carried out prior to installation.
PE pipes have been used by our customers extensively for drinking water distribution throughout Europe for over 40 years and have proven to be safe and reliable for this application. Where moderate soil contamination exists there are a number of multi-layer PE pipe solutions available from pipe manufacturers with special barrier layers incorporated into the pipe wall. These barrier layers, which are often of aluminium, whilst impermeable to contaminants are thin enough not to seriously impair the flexibility of the pipes and to allow them to be welded using electrofusion fittings.
As a matter of good engineering practice, areas of heavily contaminated soil should be avoided as a potential route for drinking water pipes of any material.