Water Purification Tablets: The Complete Guide

Water purification tablets. They're tiny, they're cheap... but they do NOT all last for years. And the wrong tablets could leave you drinking water that still has nasty stuff in it.

Let us break this down. Because this matters.

The Three Main Types

Iodine tablets (Potable Aqua)
Chlorine tablets (Aquatabs) - uses NaDCC
Chlorine Dioxide tablets (Katadyn Micropur MP1, Potable Aqua ClO2)

They are NOT interchangeable. And here's what most people get wrong: Chlorine tablets (NaDCC) and Chlorine Dioxide are NOT the same chemical. Different molecules, different effectiveness, different uses.

The Big Question: What About Cryptosporidium?

Only CHLORINE DIOXIDE kills Cryptosporidium. Not iodine. Not regular chlorine (NaDCC).

According to the CDC: "Cryptosporidium is poorly inactivated by chlorine- or iodine-based disinfection at concentrations and times practical for field water treatment."

Crypto has a tough outer shell. Regular chlorine and iodine can't penetrate it. Chlorine dioxide can - but it takes 4 HOURS.

Iodine Tablets (Potable Aqua) - ~$10/50 tablets

Kills: Bacteria, Viruses, Giardia (partially)

Does NOT kill: Cryptosporidium

Wait time: 30-35 minutes (the FASTEST option)

When to use iodine: When you need FAST disinfection and you're dealing with bacteria/viruses. Speed is the main advantage here.

The downsides:

Turns water brownish
Tastes like... iodine (neutralizer tablets available)
Don't use for more than a few weeks
Avoid if pregnant, thyroid issues, or iodine allergy
Per CDC, has "low effectiveness" against Giardia

Shelf life: The iodine tablets themselves can last years IF unopened and stored properly. Once opened, Potable Aqua says replace yearly or if tablets turn yellowish/green.

Potable Aqua Iodine Tablets on Amazon

Chlorine Tablets (Aquatabs) - ~$10/50 tablets

Active ingredient: Sodium dichloroisocyanurate (NaDCC) - this releases chlorine into water

Kills: Bacteria, Viruses, Giardia

Does NOT kill: Cryptosporidium

Wait time: 30 minutes

Better than iodine for:

Taste (much better)
Giardia effectiveness
Safe for longer-term use

Shelf life: Aquatabs strip-packed: 2-5 years. Aquatabs in tubs: 2-3 years. Check packaging for expiration.

Best for: General water treatment. Most common choice. Used by WHO, UNICEF, Red Cross.

Aquatabs on Amazon

Chlorine Dioxide Tablets (Katadyn Micropur MP1) - ~$15-20/30 tablets

This is the ONLY chemical treatment that kills Cryptosporidium.

Active ingredients: Sodium chlorite + Sodium dichloroisocyanurate dihydrate - when combined in water, these generate CHLORINE DIOXIDE (ClO2) - a completely different molecule than regular chlorine.

Kills: Bacteria, Viruses, Giardia, Cryptosporidium

Wait times:

30 minutes for bacteria and viruses
4 HOURS for Cryptosporidium

Yes, 4 hours is a long time. That's the tradeoff for complete protection.

Taste: Minimal to none. Best tasting of all three.

THIS IS THE KEY DIFFERENCE - Shelf Life

Katadyn Micropur MP1: 4-5 years sealed - This is why we recommend Katadyn
Potable Aqua Chlorine Dioxide: 4 years sealed

The much longer shelf life means you don't have to rotate as often. That matters for preps you might not touch for years.

Katadyn Micropur MP1 on Amazon - OUR PICK

Potable Aqua Chlorine Dioxide on Amazon

Timing Comparison

Type	Bacteria/Viruses	Giardia	Cryptosporidium
Iodine	30-35 min	30 min (partial)	NOT EFFECTIVE
Chlorine (NaDCC)	30 min	30 min	NOT EFFECTIVE
Chlorine Dioxide	30 min	30 min	4 HOURS

Shelf Life Comparison

Product	Shelf Life
Aquatabs (strip)	2-5 years
Aquatabs (tub)	2-3 years
Potable Aqua Iodine	Replace yearly once opened
Potable Aqua ClO2	4 years
Katadyn Micropur MP1	4-5 years (OUR PICK)

Katadyn costs more but lasts longest. When you're prepping for years, that matters.

So What Should You Buy?

Stock ALL THREE. They each have different strengths:

Iodine: FASTEST (30 min). Use when speed matters and you're not worried about Crypto.
Chlorine (Aquatabs): Good all-around, better taste than iodine, 30 min wait. Rotate every 2-3 years.
Chlorine Dioxide (Katadyn): COMPLETE protection including Crypto. 4-5 year shelf life. Put these where you don't rotate often.

We keep tablets everywhere - home, EDC, car, go bags. They weigh nothing, cost almost nothing, and could save your life.

For the Medical Professionals: If Someone Gets Cryptosporidiosis

Crypto causes severe watery diarrhea lasting 1-2 weeks. In an emergency with limited resources? Dehydration could be fatal.

Treatment: Nitazoxanide (Alinia)

This is the only FDA-approved antiparasitic for cryptosporidiosis in immunocompetent patients.

Dosing (3-day course, twice daily with food):

Age	Dose	Form
Adults and children 12+ years	500 mg every 12 hours	Tablet
Children 4-11 years	200 mg (10 mL) every 12 hours	Oral suspension
Children 1-3 years	100 mg (5 mL) every 12 hours	Oral suspension

Important: Tablets are 500 mg each - do NOT use tablets for children under 12 (dose is too high). Children must use the oral suspension.

Effectiveness: Clinical cure rates 72-88% in immunocompetent patients. Less effective in immunocompromised patients - for HIV/AIDS patients, antiretroviral therapy is the primary treatment.

Stock it: Nitazoxanide requires prescription. Talk to your doctor about keeping some on hand, especially if you have vulnerable family members.

Pro Tip: Tablets Are BACKUP

Our water prep priority:

Stored water (WaterBOB, containers)
Gravity filter (Berkey/Boroux at home)
Portable filters (GRAYL, Katadyn BeFree)
Ability to boil (Pathfinder canteen, camp stove)
Tablets (last resort chemical treatment)

Layer your systems. Every one of these can fail.

Key Takeaway

Only chlorine DIOXIDE kills Cryptosporidium (and it takes 4 hours). Stock all three types: iodine for speed, Aquatabs for general use, and Katadyn Micropur for complete protection with the longest shelf life.

Build Your Water System

Tablets are just one layer. Our free guides cover complete water storage, filtration, and purification systems.

Get the Free Guides