"Alternative" anti-scale processes: ANSES's recommendations

Today ANSES is publishing its opinion and report on so-called alternative anti-scale (Alt-AS) processes in drinking water distribution systems. The Agency stresses first of all that Alt-AS manufacturers and distributors have a responsibility to provide evidence of the safety and effectiveness of the processes and products they market, and expresses its disappointment at the limited data available in this regard. It recommends improving the information provided to consumers to enable them to make informed choices when purchasing drinking water treatment products and processes, developing the standardisation and certification of these processes, and updating the regulations.

Drinking water is a potential source of calcium, an essential nutrient for nutritional balance. However, water that contains excessive amounts of calcium, carbonates and hydrogen carbonates can also cause limescale build-up, particularly on domestic hot water circuits and equipment. This limescale can have both technical and economic consequences (hydraulic disturbances in circuits, malfunctions of equipment, higher energy consumption, shortened equipment lifespan). In order to reduce the impact of "hard" water on circuits and equipment, anti-scale water treatment products and processes (WTP&Ps) are used.

These WTP&Ps include so-called "conventional" devices, which are authorised by the Ministry of Health on the basis of a measurable effect on tap water quality (decrease in pH, and in calcium and magnesium concentrations).  The emergence and proliferation of new anti-scale processes (known as alternative or Alt-AS) led the Directorate General for Health to issue a formal request to ANSES to assess the health risks associated with their use. ANSES's expert appraisal focused on Alt-AS processes using sacrificial anode electrolysis or catalysis, techniques that may alter the chemical composition of the water.

Agency conclusions and recommendations

In the absence of sufficient data on the safety or effectiveness of these systems, whether in the scientific literature or in evidence provided by industry professionals, the Agency is unable to reach a conclusion as to the safety and effectiveness of Alt-AS processes using zinc anode electrolysis or catalysis. On the basis of the evidence at their disposal, the experts nevertheless made some recommendations for assessing the safety and effectiveness of these systems.

The expert appraisal showed that an Alt-AS treatment that effectively acts on the limescaling properties of the water can produce indirect effects on water quality by promoting the release of calcium carbonate (CaCO3) particles, increasing turbidity (the cloudiness of the water) and loosening corrosion and biofilm deposits, even if it does not alter the overall chemical composition.

In view of this observation, ANSES recommends that Alt-AS processes be required to sufficiently demonstrate their effectiveness and safety, as is the case for so-called "conventional" WTP&Ps, with regard to their potential effects on water quality, considering both direct and indirect effects.

ANSES also encourages the development of standardisation and certification, which could be the central part of a scheme for assessing and authorising devices placed on domestic circuits and used on water that already meets quality requirements.

To achieve this, ANSES also recommends updating the regulations applicable to drinking water treatment products and processes, since they do not yet take "Alt-AS" processes into account.

Lastly, the Agency stresses the need to continue and redouble efforts to provide information for users, to enable them to make informed choices when purchasing domestic WTP&Ps with regard to the quality of drinking water supplied to their tap. This broad and varied population, often lacking specialist knowledge, should be informed of:

  • the importance of understanding the quality of the drinking water supplied to their homes;
  • the need to verify the practicality of installing an additional WTP&P on a domestic system with regard to the quality of the water supply and the equipment to be protected; for example, the use of a conventional or alternative anti-scale process is rarely justified when the water hardness is less than 15°f (French degrees – unit of measurement for water hardness);
  • the effectiveness and safety of the WTP&Ps they are likely to purchase, in order to verify whether the claims of the companies marketing them are consistent with their needs;
  • the need to maintain a supply of cold water that has not undergone this treatment, for drinking and food use;
  • the technical installation rules to be observed to prevent any risk of interconnection or backflow;
  • the need for appropriate and regular maintenance of the treatment system.

Data on drinking water quality are available:

  • on the website of the French Ministry of Health: www.eaupotable.sante.gouv.fr;
  • from local town halls;
  • from water production and distribution companies;
  • on your water bill.