Chlorine in the water

Chlorine prevents proliferation of germs in water mains. It acts as a food preservative and guarantees stable sanitary quality of the water supplied to consumers.

Bacteria and other microbes are a normal part of the environment. They are present in the air and soil, and they may possibly get to the water mains, for example during piping repairs. Organic sediments inside the pipes are also an ideal environment for bacteria proliferation.

The water is of an excellent bacteriological quality when it leaves the water treatment plant, containing only elements necessary for your health: mainly salts and minerals. To maintain this quality all the way to your tap and to eliminate any risk of accidental secondary contamination, chlorine must be added to the treated water. Chlorine is added in very small doses at the water treatment plant outlet and then at various points in the distribution network. This is because chlorine content decreases during water distribution due to reactions with piping walls and other substances contained in the water, including undesirable microbes.

Reactions of chlorine with some agents naturally present in the water can give rise to various undesirable substances called generally the "chlorination by-products". Those substances are only present in treated water in trace (minimal) quantities, but less soluble chlorine derivatives can affect its taste.

To preserve bacteriological safety of water, on average 0.1 to 0.2 milligrams of chlorine per litre of water is added at various points of the distribution network. This ensures that the water that reaches you is totally compliant with sanitary regulations. Chlorine content in water treated this way represents 1 drop of chlorine per 1,000 litres of water, which is roughly equal to 5 bathtubs.

Chlorine is not detrimental to health in small quantities. It is a strong disinfectant that protects everyone from accidental secondary contamination of water.

Depending on the position in the network, the water can have a stronger or weaker chlorine smell. You can eliminate it in the following ways:

• Prior to consumption, let the water stand for a few minutes
• Prior to consumption, add a few ice cubes or lemon juice drops to the water
• Keep the water in the refrigerator in closed glass bottles (for no longer than24 hours)
• You can also boil the water briefly prior to consumption

Chlorine is volatile; therefore the above advice often suffices to eliminate its smell. If you still find a strong chlorine presence in the water, do not hesitate to contact us.

No chemical element has yet been proven to be as efficient and perfectly safe. Modern filtering methods used in water treatment enable chlorine dosage to be kept to a minimum. Sensory properties of the water (mainly taste) can be improved with ozone, which is added to drinking water at the Želivka water treatment plant. This Plant supplies water to over 60% of Prague. Ozone has only a temporary effect in securing water's safety during production, and so chlorine is added subsequently to preserve bacteriological safety throughout distribution.

Minimal chlorine dosage is defined in Public Notice No 376/2000, which stipulates the requirements for drinking water and the frequency at which these are to be monitored. The Public Notice is in harmony with the European Directive 98/83 EC on the quality of water intended for human consumption. Under the Public Notice, the minimal free chlorine content in water running from a consumer's tap must be 0.05 mg/l.