Why is chlorine added to tap water?
Ayus installs and maintains 4-stage water filters at home, hidden under the kitchen sink. One of the questions we hear most during visits is this: why does the water taste like a swimming pool?
The answer is simple. Water leaves the treatment plant clean, but it still has to travel kilometres of pipes to reach your kitchen. Chlorine is added to protect it on that journey, stopping microorganisms from growing back. It is one of the steps that keep mains water in Portugal within the law.
How much chlorine is in the water that reaches your home?
The chlorine left in the water when it comes out of the tap is called residual chlorine and is measured in milligrams per litre (mg/L). Water utilities publish these values in their quality control results, and ERSAR, the regulator, brings that information together. The values are usually a few tenths of a milligram per litre.
That is not much, but our taste and smell are sensitive. According to the World Health Organization, some people can taste chlorine from about 0.3 mg/L. People who live close to the treatment point tend to notice it more, because the water reaches them with more chlorine.
Want to know where the water in your municipality comes from and what it contains? See tap water by municipality.
How to get rid of the chlorine taste without a filter?
Free chlorine slowly evaporates when the water is in contact with the air. So there are a few home tricks that help:
- Fill a jug and leave it uncovered for a few hours before drinking.
- Then cover it and keep it in the fridge: cold water masks the taste even more.
- Add a slice of lemon or a few mint leaves, if you like.
- Change the water in the jug every day and wash it often.
How does activated carbon remove chlorine?
Activated carbon is carbon treated so that it is full of tiny pores. A single gram has a huge inner surface area. When water flows through it, chlorine and many organic compounds that cause bad tastes and smells get trapped on that surface.
That is why filter jugs and under-sink filters use activated carbon. The difference lies in the amount of carbon, how long it is in contact with the water and how often the cartridge is changed.
What does Ayus do about the chlorine taste?
In the Ayus filter, the second stage is an activated carbon cartridge. Water comes out of the 3-way tap with no chlorine taste or smell, every time you turn it on, with no waiting for the jug. Before that, a sediment filter holds back sand and rust; afterwards, ultrafiltration and the magnesium cartridge complete the journey. See how the filter works.
When the carbon reaches the end of its life, the water starts tasting of chlorine again. It is the easiest sign to notice, but you do not need to keep an eye on it: we change the filters every [INTERVALO A CONFIRMAR] and let you know beforehand.
