Dear Colleagues, I am Davis working on project and construction ...

Robert Pitchers


Dear Davis

Different types of pipe materials may be of merit depending on the particular water supply network. Networks pipes (from a treatment works to a property) may be of different materials than those used for a plumbing installation inside a building. Other factors, such as their structural integrity, may be more important than their effects on water quality.

From a microbiological point of view, non-metallic materials (e.g. plastics) for use in contact with drinking water should not exert an adverse effect on water quality by leaching compounds that could support the growth of micro-organisms. Approval schemes exist to test the suitability of non-metallic pipes (e.g. here in the UK there is British Standard BS6920 Part 2.4). No plastics material should be used that has not passed such a test.

Obviously, metal pipes do not leach organic compounds capable of supporting microbial growth. However, their surfaces can be rougher than plastics materials and can create micro-environments that can provide a sheltered habitat to permit biofilm growth.

But, what grows on a pipe is strongly influenced by the characteristics of the water supply. A water with an effective chlorine residual or without nutrients (biostable) will have a greater impact on limiting microbial growth than the type of pipe material. The converse applies.

Once inside a building, other factors become more significant. Both temperature and stagnation can exert a strong influence on water quality. There has been much debate about whether copper or plastics make better materials for plumbing installations. It has been claimed that copper can reduce biofilm formation and thus reduce the likelihood of Legionella growth. Flexible tap-connectors made from various artificial rubber materials (e.g. EPDM) have been found to support biofilm growth and have been suspected of causing infections in hospitals.

I hope this helps you to reach a decision.

Kind regards


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