Chemical treatment
Water purification tablets
Tablets that treat water chemically, viruses included. Light, compact and the obvious companion to a water filter.
Water purification tablets cover exactly the gap a membrane filter leaves open. A filter stops bacteria and protozoa down to 0.1 micron, but viruses are smaller and pass through, while chemical treatment does act on them. You dissolve a tablet in a measured volume of water, wait the stated contact time and then drink. They weigh almost nothing and take up no space, which is why they belong in every emergency kit and rucksack.
Tablets rarely replace a filter, but they almost always complement one. Treat clear water: filter first, or let sediment settle and decant, because suspended dirt reduces the effect of any chemical treatment. Stick strictly to the dose and the contact time on the packaging, as cutting the wait short undermines the result. Cold water needs longer than warm water. When you stock up, check the expiry date and keep the strips dry and out of the light. If you would rather not treat anything at all, packaged long life water is the simplest base supply to keep at home.
Frequently asked questions
A water filter rated to 0.1 micron holds back bacteria and protozoa, but not viruses. Tablets work chemically, so they also act on viruses. Filter plus tablet therefore covers more ground than either one on its own.
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