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.
By Tom Rowland · Updated 18 July 2026 · 6 products, price-tracked
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, Oasis, Puritabs — 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 Aquatabs 397mg 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.
Top pick: Aquatabs 67mg Water Purification Tablets (100 pack). 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.
| Tablet | Treats per tablet | Active agent | Pack size | Price | |
|---|---|---|---|---|---|
| Aquatabs 67mg Water Purification Tablets (100 pack)TOP PICK | 8–10 litres (clear water) | NaDCC (sodium dichloroisocyanurate) | 100 | £12.00at usual price | Check price → |
| Aquatabs 397mg Water Purification Tablets | 20 litres (clear water) | Sodium dichloroisocyanurate (NaDCC) | 100 tablets (tub) | £17.00at usual price | Check price → |
| Lifesystems Chlorine Dioxide Water Purification Tablets | 1 | Chlorine dioxide | 30 | £10.50at usual price | Check price → |
| Oasis Water Purification Tablets | 1 | NaDCC (sodium dichloroisocyanurate) | 50 | £3.99at usual price | Check price → |
| Katadyn Micropur Forte Water Purification Tablets | 1 | Sodium dichloroisocyanurate (DCCNa/chlorine) plus silver ions | 100 | £25.00at usual price | Check price → |
| Puritabs / Steritabs Water Purification Tablets | 1 | NaDCC (troclosene sodium) chlorine | 50 | £6.00at usual price | Check price → |
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Aquatabs 67mg Water Purification Tablets (100 pack)
Who it's for: A cheap, long-life chemical backup for disinfecting tap or clear water during a boil-water notice or supply outage.
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.
- Very low cost per litre and a multi-year shelf life, so one 100-pack quietly covers a household for years.
- NaDCC is the humanitarian-sector standard, effective against bacteria, viruses and Giardia with a simple 30-minute wait.
- Compact and equipment-free — dose, wait, drink — which makes them ideal for a grab bag or kitchen drawer.
- Leaves a faint chlorine taste and does nothing for sediment, chemicals or heavy metals.
- Not reliably effective against Cryptosporidium, so cloudy water must be pre-filtered first.
Don't buy if 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.
Aquatabs 397mg Water Purification Tablets
Who it's for: Disinfecting larger volumes at once — a stored water container, water butt or the household's drinking supply during a mains outage or boil-water notice.
The 397mg is the high-volume version of a genuinely trusted product: NaDCC chemistry that's WHO- and NSF-recognised, treating around 20 litres per tablet in about 30 minutes. It's the sensible choice for whole-household resilience rather than a single bottle, and a tub of 100 stores for years.
- Kills bacteria and viruses within about 30 minutes using NaDCC (sodium dichloroisocyanurate), the same chlorine-donor chemistry used by aid agencies worldwide.
- One tablet treats roughly 20 litres, so a 100-tablet tub covers a large volume cheaply, with a multi-year shelf life for a grab-bag or cupboard.
- Compact and light with far less aftertaste than old-style iodine tablets, and no special equipment needed.
- Chlorine-based tablets don't reliably kill Cryptosporidium and are less effective in cloudy water, so silty or surface water should be pre-filtered first.
- The 20-litre dose is sized for containers, not a single water bottle — using one tablet for 1 litre is wasteful and can leave a strong chlorine taste.
Don't buy if you only ever need to treat a bottle or two on the move — the smaller 8.5mg or 33mg Aquatabs (dosed for 1–5 litres) are far less wasteful; and if your likely risk is Cryptosporidium in stream or flood water, pair tablets with a physical filter or choose a different method.
Lifesystems Chlorine Dioxide Water Purification Tablets
Who it's for: A compact chemical backup for a grab bag, treating clear water on the move.
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.
- Chlorine dioxide tackles bacteria, viruses and the tougher cysts (Cryptosporidium, Giardia) that some cheaper tablets do not
- Very little chemical aftertaste compared with standard chlorine tablets
- Individually foil-sealed tablets with roughly a 3-year shelf life, so they store well in a kit
- One tablet per litre means 30 tablets only treat 30 litres, which is modest for a household or a long outage
- You wait 10-30 minutes per litre and should pre-filter cloudy water first, so it is slower and fiddlier than a pump or gravity filter
Don't buy if 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.
Oasis Water Purification Tablets
Who it's for: A cheap, compact, long-life backup for disinfecting clear water in a grab bag or camping kit.
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.
- Very low cost per litre and a long shelf life, so they sit in a kit for years without fuss
- Lightweight and compact NaDCC tablets, well proven and widely used by the military and aid agencies
- Effective against bacteria, viruses and many protozoa in clear water when used correctly
- Leaves a mild chlorine taste and does not remove chemicals, heavy metals or sediment
- You must pre-filter cloudy water and wait the full 30 minutes, so they are slower and less convenient than a pump filter
Don't buy if 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.
Katadyn Micropur Forte Water Purification Tablets
Who it's for: A compact, long-shelf-life water backup for a grab bag or travel where you cannot boil or filter.
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.
- Each tablet treats 1 litre and the pack covers 100 litres in a very small, light package
- Silver ions keep treated water safe for months, so it doubles as a stored-water preserver
- Roughly 5-year shelf life makes it a genuine set-and-forget grab-bag item
- 30-minute wait for bacteria and viruses, and up to 2 hours for Giardia in cold or cloudy water
- Like all chlorine-based tablets, it does not reliably kill Cryptosporidium and won't remove silt, chemicals or bad taste
Don't buy if 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.
Puritabs / Steritabs Water Purification Tablets
Who it's for: A cheap, pack-anywhere backup for disinfecting tap water during a boil-water notice or supply-contamination event.
A proven, inexpensive way to make questionable clear water safe to drink when the mains supply is compromised. They reliably kill bacteria and viruses, but they disinfect rather than filter, so pair them with a filter or a cloth pre-strain if the water is cloudy.
- Very cheap and compact: a 50-tablet pack costs only a few pounds and stores for years, so it easily earns a place in a grab bag or under-stairs kit.
- Uses NaDCC, the same WHO-recommended chlorine chemistry issued to the military and aid agencies, and is effective against bacteria and viruses.
- Long shelf life (around 5 years foil-packed) and no kit required: add one tablet per litre, wait about 30 minutes, drink.
- Leaves a faint chlorine taste and needs a 30-minute wait; it disinfects but will not remove sediment, chemicals or heavy metals.
- Less reliable against Cryptosporidium, so it is not a full substitute for a filter when water is genuinely dirty.
Don't buy if Don't rely on these alone if your only water is visibly dirty, silty or chemically contaminated: that calls for filtering or boiling. Also check what you are buying, as the Puritabs name is now widely sold as a WaterRower tank-cleaning biocide that is not for drinking.
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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.