Rainwater can be made drinkable, but only by following some treatment phases, with a complete filtration and disinfection process, as it may contain bacteria, viruses, heavy metals and air pollutants.
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When can it be harvested?
Not all rainwater can be treated to make it drinkable. In fact, rainwater to be made drinkable must be collected away from industrial or otherwise polluted areas (e.g., heavily trafficked roads), on roofs that can be made of metal, tile, or concrete. The gutter must be clean and a filter first flush It is used to discard the first rain, the dirtiest one.
Filtering
After collection, rainwater must be filtered to make it drinkable. Filtration follows several stages, exactly as in aqueducts:
- Leaves, sand, coarse dust and insects are eliminated through grids, filters and decanters.
- Subsequently, mechanical filtration (with ceramic, hollow fiber, or cartridge filters) eliminates algae, fine sediment, and bacteria.
- Finally, activated carbon removes pesticides, organic compounds, heavy metals, odors and flavors.
Disinfection
Once the water has been well filtered, we move on to the actual disinfection, which can take place:
- With boiling: bringing the water to a boil for 1-3 minutes.
- With chlorine: 2-4 drops per liter. A slight chlorine taste should remain; otherwise, add another 1-2 drops.
- With the UV lamp which kills microorganisms without altering the taste of the water.
Drinkability requirements
Once the rainwater has been filtered and disinfected, it will be necessary to check its correct drinkability values.
The latest limits were introduced in 2026, and to be considered drinkable, water must meet certain parameters, the most important of which are:
- Absence of emerging contaminants: Strict monitoring of substances such as PFAS (limit “total PFAS” of 0,5 µg/l).
- Microbiological parameters: Total absence of dangerous bacteria, viruses or parasites.
- Chemical and physical parameters: The pH should be between 6,5 and 9,5, with strict limits for heavy metals such as lead, iron and manganese.
If you intend to continuously use rainwater transformed into drinking water thanks to your system, the laboratory analyses, which guarantee the safety values, they must be done periodically.
Food container
Once rainwater becomes drinkable, it should be stored in clean, closed containers, avoiding prolonged stagnation and protected from light and heat sources.
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