How to make water safe: step-by-step guide
⏱ 2 min read
Boiling, tablets, filters, sunlight. A guide based on official advice. The same text is in the free SurvivalZone.app and works without internet.
First
- Use the cleanest water you have: rainwater, tap water after an outage, a spring. Avoid standing water near roads, fields and factories.
- Strain cloudy water through a clean cloth, a coffee filter or several layers of kitchen paper, then let it settle for 30 minutes.
Methods
- Boiling: bring to a rolling boil and keep it boiling for at least 1 minute. The most reliable way to kill bacteria, viruses and parasites.
- Water purification tablets: dose and wait exactly as the manufacturer says.
- Unscented household bleach, plain sodium hypochlorite (about 5–6%): 2 drops per litre, stir and wait 30 minutes. The water should smell slightly of chlorine. Double the dose if it is cloudy.
- Camping filter: removes bacteria and parasites but usually not viruses. Best combined with boiling or tablets.
- Sunlight (SODIS method): a clear PET bottle up to 2 litres, clear water, 6 hours in full sun or 2 days if cloudy.
Storage
- Keep treated water in clean, closed containers in a cool, dark place.
- Stock: 3 litres per person per day, for at least 3 days.
Watch out
- Boiling and tablets do not remove chemicals, fuel or heavy metals. Do not drink water that smells or looks like that.
- Avoid flood water, even boiled, if you have any other option.
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Sources
- BBK guide "Vorsorgen für Krisen und Katastrophen" (Germany)
- Polish government safety guide (MON, MSWiA, RCB, 2025)
- WHO: water, sanitation and hygiene in emergencies
Scientific literature and guidelines
- Cochrane review (Clasen et al., 2015): interventions to improve water quality for preventing diarrhoea
- US EPA: emergency disinfection of drinking water
- WHO: Guidelines for drinking-water quality, 4th edition with first and second addenda
Official sources are checked automatically every day. Last check: 2026-11-08.
General guidance only; it does not replace the emergency services. If a life is in danger, call 112.
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