Best water purification tablets for emergencies (2026)
Purification tablets are the cheapest, longest-lasting way to make clear water safe to drink when you can't boil it — a power cut with an electric hob, an off-grid trip, or a supply you're unsure about. They're small, they store for years, and a single pack quietly covers a household. Here's how the main types compare, and the important limits on what they can and can't do.
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By Tom Calder · Updated 5 November 2026 · 5 products, all price-tracked
Our picks
Photo: AmazonBiox Aqua Chlorine Dioxide Tablets
A compact chemical backup for a grab bag, treating clear water on the move.
as of 5 Nov 2026, 22:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.
Photo: AmazonKatadyn Micropur Forte Water Purification Tablets
A compact, long-shelf-life water backup for a grab bag or travel where you cannot boil or filter.
as of 5 Nov 2026, 22:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.All 5 compared
Photo: AmazonOur top pickA compact chemical backup for a grab bag, treating clear water on the move.
as of 5 Nov 2026, 22:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.Our verdict
Chlorine dioxide is the most capable chemical option for a kit like this, dealing with Cryptosporidium and Giardia that older iodine and chlorine tablets can miss, and it leaves little of the usual pool-water aftertaste. Individually foil-wrapped with a long shelf life, it is a sensible, low-cost item to keep in a grab bag.
Worth knowing: One tablet per litre means 30 tablets only treat 30 litres, which is modest for a household or a long outage
Who shouldn't buy it: Don't buy these if your aim is to supply a whole household through a prolonged outage or to remove chemical contaminants or heavy metals; tablets only handle microbes in modest volumes, so a stored-water container plus a gravity or pump filter is the better backbone, with tablets as a light top-up.
Read the full review →Photo: AmazonRunner-upA compact, long-shelf-life water backup for a grab bag or travel where you cannot boil or filter.
as of 5 Nov 2026, 22:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.Our verdict
A dependable chlorine-and-silver tablet that makes clear water microbiologically safe with a 30-minute wait, and the silver keeps treated water fresh for storage. Reliable and pocketable, but it is a disinfectant, not a filter.
Worth knowing: 30-minute wait for bacteria and viruses, and up to 2 hours for Giardia in cold or cloudy water
Who shouldn't buy it: Your likely water is cloudy, silty or from a source where Cryptosporidium is a concern — pair it with, or choose, a proper mechanical filter instead of relying on tablets alone.
Read the full review →Sold out right now (3)
The shop says these are sold out today. We check stock every hour, and each one moves back up the list when it returns.
A cheap, compact, long-life backup for disinfecting clear water in a grab bag or camping kit.
Our verdict
These are the familiar British Army-issue NaDCC tablets: simple, reliable and inexpensive, treating one litre per tablet in about 30 minutes. For emergency drinking-water backup they are hard to fault, provided you understand what chlorine can and cannot do.
Worth knowing: Leaves a mild chlorine taste and does not remove chemicals, heavy metals or sediment
Who shouldn't buy it: Don't rely on these alone if your likely water source is cloudy, chemically contaminated or you want better-tasting water. Pair them with a physical filter, and remember that during a UK boil-water notice simply boiling tap water is free and effective.
Read the full review →
A cheap, long-life chemical backup for disinfecting tap or clear water during a boil-water notice or supply outage.
Our verdict
A trusted, WHO-listed NaDCC tablet that reliably disinfects clear water against bacteria, viruses and Giardia for a few pence a dose. Sensible belt-and-braces cover for a home emergency kit, provided you understand it treats water rather than filtering it.
Worth knowing: Leaves a faint chlorine taste and does nothing for sediment, chemicals or heavy metals.
Who shouldn't buy it: Don't rely on these alone if your likely water source is cloudy, river or flood water — tablets won't remove silt, chemicals or Cryptosporidium, so pair them with a filter or choose a filter straw/gravity system instead.
Read the full review →
Disinfecting larger volumes at once: a stored water container, or the household's drinking supply during a mains outage or boil-water notice.
Our verdict
The high-volume version of a long-trusted tablet: one 167mg Oasis tablet treats 20 litres in about 30 minutes, so a pack of 100 covers up to 2,000 litres. It's the sensible choice for whole-household resilience rather than a single bottle, and it stores for years.
Worth knowing: Chlorine tablets don't reliably kill Cryptosporidium and work less well in cloudy water, so filter silty or surface water first
Who shouldn't buy it: You only need to treat a bottle or two on the move: a one-litre tablet is far less wasteful. If Cryptosporidium in stream or flood water is the worry, pair tablets with a physical filter or choose a different method.
Read the full review →ⓘ As an Amazon Associate, PreparedBritain earns from qualifying purchases. We may earn a commission when you buy, or a fee when you request a quote, through our links. When two products are close, commission can decide which one we pick. A clearly better product always wins. Amazon prices come from Amazon's own product data and show the date and time they were retrieved. Prices at other retailers are checked by us, less often. Prices and stock can change at any time, so always check the retailer's price before you buy.
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Before you buy
First, what tablets do: they chemically disinfect clear water, killing bacteria and viruses so it's safe to drink.
What they don't do is remove sediment, chemicals, heavy metals or improve taste — and standard chlorine tablets aren't reliable against Cryptosporidium. So they're a treatment for biologically-suspect but otherwise clear water, not a fix for muddy, flood or chemically-contaminated water.
There are two chemistries worth knowing.
NaDCC (sodium dichloroisocyanurate) tablets — Aquatabs and Oasis — are the humanitarian and military standard: cheap, effective against bacteria and viruses, with a faint chlorine taste. Chlorine dioxide tablets — Lifesystems, Katadyn Micropur Forte — cost more but also tackle the tougher cysts including Cryptosporidium, with less aftertaste. Avoid old-style iodine tablets: they've effectively left UK shelves and aren't suitable for everyone.
Match the dose to the job.
Small tablets treat 1 litre each (good for bottles and grab bags); large tablets like Oasis 167mg treat around 20 litres each (good for filling a stored container). Whatever you buy, respect the contact time — typically 30 minutes, longer for cold or cloudy water — and pre-filter anything that isn't clear.
We verify every product's specifications against at least two independent sources, re-check its UK price and stock on a schedule where we can track it automatically, and cross-check safety-relevant claims against official guidance. Every review is labelled Researched or Used and reviewed by us: where we've bought a product, or been sent it free, and used it ourselves, its review says which; where we haven't, our verdict is a considered spec-and-evidence comparison, not a hands-on test. When two products are close, commission can decide which one we pick. A clearly better product always wins. Read our full methodology →
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Common questions
Do water purification tablets make any water safe to drink?
No. They disinfect clear water against bacteria and viruses, but they don't remove sediment, chemicals or heavy metals, and standard chlorine tablets aren't reliable against Cryptosporidium. Cloudy, flood or chemically-contaminated water needs filtering or a different approach.
Are tablets better than boiling in a boil water notice?
No — if you can boil, boiling is free and highly effective, and it's the official advice in a UK boil water notice. Tablets are for when you can't boil (no power or gas), for off-grid water, or as cheap backup in a kit.
What's the difference between NaDCC and chlorine dioxide tablets?
NaDCC tablets (Aquatabs, Oasis) are cheap and effective against bacteria and viruses, with a mild chlorine taste. Chlorine dioxide tablets (Lifesystems, Katadyn Micropur Forte) cost more but also handle tougher cysts like Cryptosporidium and taste cleaner.
How long do purification tablets take to work?
Typically around 30 minutes of contact time for clear water, and longer for cold or slightly cloudy water. Always pre-filter anything that isn't clear, and follow the pack instructions for the dose and wait time.
Are iodine tablets a good option?
No — iodine tablets have effectively left UK shelves, aren't suitable for pregnant women, people with thyroid conditions or long-term use, and taste unpleasant. Stick to NaDCC or chlorine dioxide tablets.
How long do tablets keep in storage?
Sealed, most have a multi-year shelf life (often around 3–5 years), which is why one pack sits happily in a grab bag or kitchen drawer for years. Check the expiry date and rotate stock occasionally.
