Water Purification Without Infrastructure: Boil, Filter, Treat
Tap water can stop or turn unsafe in hours. Here is how to store what you have without poisoning yourself, replace it from rain, rivers and snow, and make any of it drinkable.
Storage: keep water from becoming poison
Use clean containers — wash bottles and jerry cans before filling. Seal tightly; cover a filled bathtub with film or clean cloth against dust and insects. Store cool and out of sunlight, away from radiators. Never keep all your water in one container — spread it across several, so one spoiled vessel doesn't cost you everything. Boil anything that has stood more than three days or came from a bathtub or boiler.
Replacing your supply
Rainwater: collect from gutters or buckets, but discard the first 5–10 minutes (it rinses dust off the surface). Boil 10 minutes, filter through cloth. Watch for roof contamination and, in industrial zones, acid rain.
Open water (river, pond): collect away from the shore and upstream of any town or industry. Cloth-filter, then boil at least 10 minutes. Assume a high chance of chemical pollution.
Snow / ice melt: avoid yellow, grey or roadside snow. Melt indoors, boil 5–10 minutes. Melted snow is mineral-poor — add a pinch of salt per litre.
The purification ladder
- Boiling is the gold standard for biological safety: a rolling boil for 5–10 minutes kills bacteria, viruses and protozoa. It does not remove chemicals or heavy metals.
- Cloth filtration removes sediment and should come before boiling, not instead of it.
- Chemical treatment (unscented bleach or purification tablets) is the backup when you can't boil — follow the dose and wait time exactly.
Boiling handles living threats; nothing simple removes chemical contamination, so where you collect matters as much as how you treat it.