Water purification tablets in Australia: Aquatabs for the kit, Katadyn for the tank, chlorine dioxide for Cryptosporidium

Water purification tablets are the backup plan: a measured dose of chlorine or chlorine dioxide that makes a litre of clear water safe to drink in half an hour, with no stove, no power and nothing to break. For the first-aid kit, the car and the bushfire box, buy Aquatabs: $15.49 for 50 tablets at Chemist Warehouse on 1 November 2026, one tablet per litre, 30 minutes, with efficacy figures Aquatabs publishes against the US EPA purifier test. For a caravan tank or stored emergency water, Katadyn Micropur Forte adds silver so the treated water keeps for up to six months. And if Cryptosporidium is the worry, the health guidance is plain that chlorine isn’t the answer; read on.

Which water purification tablets should you buy?

Buy by what you’ll treat and how long you can wait. Clear water from a town supply on a boil-water alert, a hotel tap overseas or a creek on a day walk: Aquatabs or the Lifesystems chlorine tablets, both one tablet per litre, both chlorine, both cheap. Aquatabs’ page quotes 99.9999% of bacteria, 99.99% of viruses and 99.9% of Giardia cysts in 30 minutes, tested to the US EPA purifier challenge, and Chemist Warehouse sells 50 for $15.49. Lifesystems’ 60-pack is $9.95 at Paddy Pallin with a five-year shelf life, but its listing gives no contact time or percentages, so Aquatabs is the pick when you want the numbers.

Water you’ll store, in a caravan tank or drums for a cyclone or bushfire season: Katadyn Micropur Forte (the Ef-Chlor 4 g tank tablet, which doses 1,000 to 1,200 L in one go, was currently unavailable on Amazon Australia on 11 November 2026). Its silver ions keep the treated water free of regrowth for up to six months, by Katadyn’s account, which plain chlorine doesn’t; the trade is 120 minutes before amoeba and Giardia are covered. $49 for 100 tablets at Snowys, $54.95 at Paddy Pallin, and the Micropur Forte liquid does 1,000 L from a 100 mL bottle for $54.95 if you’re dosing a tank rather than a bottle.

Water from a source where Cryptosporidium is plausible, which in Australia means farm run-off, stock, or a tank with animal access: Lifesystems chlorine dioxide. enHealth’s rainwater guidance says “chlorination is effective against harmful bacteria, many viruses and Giardia but it has limited effect against Cryptosporidium”, and chlorine dioxide is the chemistry sold for that gap. Lifesystems’ listing claims bacteria, viruses and cysts “including Giardia and Cryptosporidium”, with little aftertaste. It’s $31.95 for 30 L, the dearest per litre here, and the listing omits the contact time, which for chlorine dioxide against cysts is typically hours, so read the foil before you trust a half-hour wait.

What tablets can’t do, and when to boil instead

Tablets disinfect; they don’t filter. Dirt, leaves and silt use up the chlorine and shield organisms from it, which is why Aquatabs’ directions say to let dirty water settle or pour it through a fine cloth and then use two tablets, and why Katadyn says “for clear water”. They also do nothing to chemicals, salt or metals, so a tablet in bore water fixes the microbes and leaves the iron and the salinity exactly where they were; our bore water guide covers that.

If you have a stove or a kettle, boil. enHealth says “bringing water to a boil can disinfect rainwater”, that “boiling does not have to be maintained for any length of time”, that “kettles with automatic shut-offs are suitable for this purpose”, and that boiling “will kill any harmful bacteria, viruses and protozoa including Giardia and Cryptosporidium”. That’s a stronger claim than any tablet makes, including the chlorine dioxide one, and it costs nothing. Tablets are for when boiling isn’t possible, and as the thing in the kit that still works when the stove doesn’t.

Tablets and rainwater tanks

People buy tablets to dose a tank, and the guidance is cautious about it. enHealth says “regular chlorination of rainwater held in domestic tanks is not considered appropriate in most cases and is generally only recommended as a remedial action”, because “the effectiveness of chlorine is short lived and it will only act on water in the tank at the time of dosing. Fresh run-off into the tank after chlorination will probably not be disinfected.” For a one-off clean-up after contamination, chlorine is the tool, and enHealth’s tables say to disinfect the tank with chlorine and flush the chlorinated water. For everyday drinking from a tank, the continuous answer is a filter and a UV lamp, which our rainwater tank and UV guides cover, and the Katadyn liquid is the practical dose for a caravan tank you empty and refill.

Using them properly

One tablet, one litre, clear water, the full wait, lid on. Katadyn’s instructions put bacteria and viruses at 30 minutes and amoeba and Giardia at 120; Aquatabs says 30 minutes and the water is safe to drink. Cold water slows every chemical disinfectant, so give it longer in winter. Keep tablets in the foil until you use them: Lifesystems quotes two years unopened for chlorine dioxide and five for chlorine, Katadyn five for tablets and two for the liquid, and Aquatabs’ pages we read didn’t state one, so write the date on the pack. Aquatabs’ label warns the tablets cause serious eye irritation and are toxic to aquatic life, and must not be swallowed whole. For the chlorine taste, let the water stand open after the contact time or drink it through a carbon filter bottle, after the wait, not before.

The one trap

Treating cloudy water with one tablet and a 30-minute wait, then drinking it. Every label on this page assumes clear water; the dose and the time are set for it. Cloudy creek or tank water needs settling or a cloth filter first, a double dose by Aquatabs’ directions, and the longer wait for cysts. If you can see the dirt, the tablet is fighting the dirt, not the germs.

What we left out and why

• Aquatabs on Amazon Australia. The listing there is a US boat-and-RV 100-tablet pack that was unavailable on 1 November 2026; buy Aquatabs from a pharmacy.
• Ef-Chlor 17 mg and 33 mg tablets (Amazon Australia). Mid-size NaDCC tablets for 4 to 8 L; the 4 g tank tablet was unavailable when we checked on 11 November 2026, so for a whole tank use the Micropur Forte liquid.
• Pool and spa chlorine tablets (Bunnings). Bunnings’ search for purification tablets returns only pool chemicals; they are not dosed for drinking water.
• Steripen UV pens (Paddy Pallin, Amazon). A different method, covered in the UV guide’s notes.
• Aquatabs 1.67 g and 8.68 g tank tablets. Listed on Aquatabs’ site for 200 and 1,000 L, but we found no Australian retail page with a price on the day.
• Iodine tablets. Not stocked by the retailers we checked.