Since the time of the old Romans, metals have been used for domestic water supply installations. In recent decades, however, the metal equipment has been more and more replaced by polymer solutions as these new generation materials have doubtlessly some strong advantages over metal.

These advantages of polymer solutions over metal are mainly :

• Corrosion resistance : Metals are sensitive to oxidizers such as sodium hypochloride which is widely used for sanitation of tap water. In the case of stainless steel, the tab water can provoke sooner or later the formation of rust in the installation. In the case of brass being an alloy of copper and zinc, this sensitivity gives rise to galvanic corrosion within the brass leading to dezincification and the formation of microporous holes in the installation. In the case of multilayer pipes with aluminum the usage of brass fittings can lead to an electric potential between the aluminum and the brass and subsequent galvanic corrosion of the aluminum.
• No scale deposit : Tab water - depending on its hardness level - contains a more or less high amount of calcium and magnesium carbonate which can easily precipitate. This precipitate, well known as scale, sticks strongly to metal surfaces. Scale deposit is much lower on polymer surfaces due to their high smoothness and low surface tension.
• No biofilm adhesion : Due to the high surface smoothness achievable with polymers where biofilm adhesion is very much suppressed. This leads to less bacteria, even in case of dead zones, and thus to cleaner water.
• No contamination by heavy metals : For evident reasons there is no contamination of the tab water with heavy metals by polymeric installations which is in contrast to the situation for metal installations.
• Easy assembly : Assembly of metal installations usually comprises hot gas welding at higher temperature. For systems based on multilayer pipes and polymeric fittings a wide variety of fixation systems is on the market for professionals as well as for do-it-yourself purposes. No welding is anymore needed.
• Low noise : Polymeric piping systems do transmit less the noise of water. This is important for waste water pipes. For pressure piping systems however, it only plays a role in case of connections to older installations with a different diameter.
• Good thermal insulation : The thermal conductivity is a factor 100 to a factor 1000 lower for polymers than for metals used in plumbing. These “intrinsic” insulation properties make polymers the material of choice in particular for hot water distribution and heating systems.
• Lower cost :  The cost of fittings made with corrosion resistant metals (in particular brass) in comparison with  polymer fittings is more than 50% higher. This cost difference is partly due to the metal prices which increased by more than 20% per year during the last years, while prices of polymeric raw material remained approximately at the same level. The second important factor is the manufacturing cost. Metal fittings have to be cast in molten state meaning at more than 1000°C into the mold while polymeric fittings are injection molded at approximately 200°C. This brings important energy cost saving in the case of polymeric solution.