French and European standards on chlorine in drinking water
Chlorine is widely used to disinfect drinking water and eliminate bacteria, viruses and other microorganisms. Its presence in tap water is therefore normal, but it is regulated in order to guarantee both health safety and consumer comfort (taste, odor, tolerance).
In France: residual free chlorine in the tap
In France, the health authorities (ARS) regularly monitor the quality of the water distributed. For residual free chlorine, that is to say the chlorine still active at the tap, the values commonly used as quality benchmarks are:
- Around 0.1 to 0.2 mg/L at the tap: level generally considered sufficient to guarantee disinfection while limiting the impact on taste and the odor.
- Values which can go up to 0.5 mg/L may be tolerated occasionally, for example in certain long or sensitive networks, in order to maintain effective disinfection to the most distant points.
The controls relate both to the effectiveness of disinfection (absence of pathogenic germs) and to comfort parameters (flavor, odor, possible irritation in the most sensitive people).
At European level
At European Union level, the quality of drinking water is regulated by a directive on water intended for human consumption. This sets result requirements (absence of dangerous micro-organisms, limits for disinfection by-products, etc.), and leaves Member States a certain margin to define the levels of residual chlorine adapted to their networks.
In practice, many European countries align themselves with values close to those observed in France, with concentrations of residual free chlorine frequently located between 0.1 and 0.5 mg/L, depending on:
- the length and complexity of the network,
- the quality of the raw water and the treatments applied,
- the health safety objectives set by local authorities.
Orders of magnitude: what does 0.1 mg/L represent?
These numbers may seem abstract. To give an idea, a concentration of 0.1 mg/L corresponds to approximately 0.0001 gram of chlorine per liter of water.
We can illustrate it pictorially: it is of the order ofa single drop of chlorine in approximately 1,000 liters of water. This is very small in quantity, but sufficient to maintain a residual disinfectant effect in the network.
Why filter chlorine at home?
Even if these levels comply with health requirements, many consumers choose to install a filtration system at home to:
- significantly reduce the taste and odor of chlorine,
- improve the comfort of daily consumption (drinks, cooking, tea, coffee),
- limit exposure to disinfection by-products when water is highly chlorinated.
Domestic filtration thus makes it possible to maintain the safety linked to the disinfection of network water, while providing water that is more pleasant to drink on a daily basis.
