The short answer
A filter straw strains germs out as you drink. It works instantly with no chemicals or wait, but it doesn't handle viruses, chemicals or salt. Purification tablets are a chemical disinfectant. They kill bacteria and viruses, but take time to work, are weaker against some parasites, and don't remove dirt or chemicals. Boiling kills all three kinds of germs. Stored water beats all of them.
"Filter" and "purifier" get used like they mean the same thing. They don't, and the difference matters when you're deciding what goes in the go-bag. Here's what each one actually does, based on CDC and EPA guidance rather than what's printed on a box.
The three kinds of germs
Water from a lake, creek or broken main can carry three kinds of germs, from biggest to smallest:
- Parasites (protozoa) like Giardia and Cryptosporidium. The biggest, and the toughest against chemicals.
- Bacteria like E. coli. Smaller.
- Viruses like norovirus. Far smaller, small enough to slip through ordinary filters.
A filter works by size: it blocks what's bigger than its pores. A chemical works by killing: it's strong against some germs and slow against others. That's why they're good at different things.
Side by side
From CDC's guide to treating water when hiking, camping and traveling:
| Method | Parasites | Bacteria | Viruses | Wait | Removes chemicals or salt? |
|---|---|---|---|---|---|
| Boiling | Yes | Yes | Yes | Rolling boil 1 min, then cool | No |
| Filter straw / portable filter | Most filters, yes | Only filters with fine enough pores (0.3 micron or smaller) | No (only reverse osmosis) | None | No |
| Chlorine or iodine tablets | Poor | Yes | Yes | Per label | No |
| Chlorine dioxide tablets | Giardia yes; Cryptosporidium somewhat | Yes | Yes | Per label (longer for Cryptosporidium) | No |
| Stored or bottled water | Already safe if stored properly | None | n/a | ||
CDC's advice for backcountry water is to filter first, then disinfect: the filter handles the parasites the chemicals struggle with, and the chemical handles the viruses the filter can't.
When a filter straw makes sense
- You're away from home (car, trail, evacuation) and the only water around is a fresh-water lake, pond or creek.
- You need to drink now, not in 30 minutes.
- You want something light that fits in a glovebox and uses no chemicals.
Its limits are real: it won't handle viruses, it won't touch fuel, pesticides or other chemicals, and it won't make salt water drinkable. Murky water clogs it faster, so let water settle or pre-filter it through a clean cloth first.
When tablets (or bleach) make sense
- Your town issues a boil-water notice and you can't boil (no power, no gas).
- You're treating a jug or pot of water for the household, not one drink at a time.
- The water may carry viruses, for example after a water-main break or sewage backup.
Use tablets exactly as the label says, check the expiration date, and expect a chlorine taste. At home, plain unscented household bleach works too. The EPA's directions: 8 drops of 6% bleach (or 6 drops of 8.25%) per gallon, stir, and let it stand 30 minutes. Double it if the water is cloudy, colored or very cold. It should smell slightly of chlorine; if it doesn't, repeat the dose and wait 15 more minutes.
What neither one fixes
The plan we'd actually use
- Store water first. 1 gallon per person per day for at least three days. A family of four needs 12 gallons.
- Know how to make more safe at home: boil it, or use unscented bleach per the EPA directions above.
- Carry a backup: a filter straw in the go-bag and the glovebox, plus tablets if you want virus protection on the road.
About our filter straws
Our Water Filter Straws (2-pack) use a hollow-fiber membrane; the supplier's spec sheet lists the membrane at 0.01 micron. We sell them as what they are: a filter for fresh water sources, used as directed. We don't call them purifiers, we don't claim they remove viruses, chemicals or salt, and we won't publish removal percentages or a filter-life number until we have an accredited lab report for this exact model. We don't sell purification tablets; pick them up at a pharmacy or outdoor store, and look for an EPA registration number on the package.
Water Filter Straws (2-pack)
$29.95Hollow-fiber membrane filter straws for fresh water sources. A filter only, not a purifier.
See what's insideDatrex Water Pouches (12-pack)
$19.95Sealed 125 mL drinking-water pouches, 1.5 L total. Add-on: ships with a kit or core item.
See what's inside72-Hour Go-Bag for Two
$199.95Weather radio, 2 food rations, 12 water pouches, 2 filter straws, light, warmth, tools and dry bags in one backpack.
See what's insideBuilding the rest of your kit? See the 72-hour emergency kit checklist.
Sources
- CDC: Water Treatment Options When Hiking, Camping or Traveling
- CDC: How to Make Water Safe in an Emergency
- EPA: Emergency Disinfection of Drinking Water
- Ready.gov: Build a Kit
Questions people ask
Does a water filter straw remove viruses?
Generally, no. CDC's guidance is that portable filters can remove parasites, and filters with small enough pores can remove bacteria, but only reverse-osmosis systems remove viruses. Our straws are filters, not purifiers, and we don't claim they remove viruses.
Do purification tablets work on everything?
No. CDC says chlorine and iodine work well on bacteria and viruses but poorly on parasites like Cryptosporidium, and chlorine dioxide does somewhat better on Cryptosporidium with a longer wait. Tablets also don't remove dirt or chemicals.
Can I drink flood water if I filter it?
No. Flood water can carry fuel, pesticides and sewage. Neither a filter straw nor tablets remove chemicals. Use stored water, bottled water, or water your local officials say is safe.
Can a filter straw make salt water drinkable?
No. Filter straws and tablets don't remove salt.
What's the best emergency water plan?
Stored water first: 1 gallon per person per day for at least three days. Then a way to make more water safe: boiling, unscented bleach per EPA directions, or tablets. A filter straw is a lightweight backup for go-bags and cars.