exogenic pollution

The materials forming part of some compounds used in water treatment or distribution ("rubber" in seals, solvents used in paint and coatings applied to structures, monomers and additives used to produce plastic pipes…) can cause pollution.

Some of these materials will be more or less toxic, others will simply release organic carbon that is likely to be used as a nutrient by common bacteria and promote their proliferation through the distribution network. Some countries (USA, EU) have published a list of products that must be banned from the production of any unit entering into contact with water and of tests used to obtain approval for others.

Similarly, materials used in pipes and/or taps and valves can be attacked by water (corrosion) and release metals of which the most dangerous is lead (risk of saturnism). Additionally, new European legislation requires that, by 2013, water delivered at the consumer’s tap will contain less than 10 µg·L^–1 of Pb; this requirement involves major investment in replacing, lining and isolating old lead branch pipes.