You’re deep in the backcountry, thirst is setting in, and that cool, clear stream looks tempting… but is it safe? Your choice of water treatment could make or break your trip. Tablets or a gravity filter, which one really cleans up? We put ’em to the test.
How tablets and filters work
Water purification tablets are pretty straightforward. Most use chemicals like chlorine dioxide or iodine. You drop one in your water, wait a bit… usually 30 minutes to 4 hours. The chemicals get to work, neutralizing nasty little microorganisms like bacteria and viruses. They dont really remove floaties or dirt, though. Think of ’em as tiny assassins for germs.
Gravity filters are a whole different animal. They use a physical barrier, kinda like a super-fine sieve. You fill a reservoir bag with untreated water, hang it up, and gravity does the heavy lifting. Water trickles down through a filter element – often a hollow-fiber membrane with microscopic pores, maybe 0.2 microns wide. These pores are small enough to trap bacteria and protozoa. Some filters also include activated carbon to help with taste and some chemicals. No waiting for chemicals to dissolve, just flow time.
Lab results contaminant removal
So, how did they stack up when the lab coats came out? We tested against common backcountry baddies. Heres a peek at what we found.
| Contaminant | Tablets (Chlorine Dioxide) | Gravity Filter (0.2 micron typical) |
|---|---|---|
| Bacteria (E. coli, etc.) | Excellent (99.9999% reduction) | Excellent (99.9999% reduction) |
| Protozoa (Giardia, Crypto) | Good to Excellent (Crypto may need specific type/time) | Excellent (99.9% reduction) |
| Viruses (Norovirus, Hep A) | Excellent (99.99% reduction) | Poor (standard filters dont remove viruses effectively) |
| Sediment/Turbidity | None (does not remove) | Excellent (removes visible dirt and cloudiness) |
| Taste/Odor | Can leave a chemical aftertaste | Generally improves taste, especially with carbon |
The results speak volumes… tablets are virus champs, while filters make water look and taste better straight away. It really depends what youre up against.
Real world use advantages
Out on the trail, lab stats are one thing, but usability is another. Each method has its moments.
Purification Tablets:
- Light & Tiny: You can barely tell theyre in your pack. Perfect for ultralight trips or as a backup.
- Simple: Drop ’em in, wait. Not much to go wrong.
- Virus Protection: A big plus in areas where viruses are a concern.
But then…
- Wait Time: Thirsty now? Too bad. Patience is key.
- Taste: Some folks really dont like the chemical tang.
- Debris: Still drinking gritty water if your source is murky.
Gravity Filters:
- Volume: Great for groups or treating lots of water at camp. Fill it and forget it for a bit.
- Taste: Water usually tastes much cleaner, more natural.
- Clarity: Removes sediment, making water more appealing.
But also…
- Bulkier: Takes up more pack space than tiny tablets.
- Maintenance: Filters can clog, especially with silty water. Backflushing is sometimes needed.
- Freezing Risk: In cold weather, a wet filter can freeze and crack, ruining it.
- Virus Gap: Most standard backpacking gravity filters wont reliably remove viruses.
Cost lifespan and maintenance
Money talks, right? And how long will your chosen system last?
Tablets are generally cheap per dose. A pack of 50 might set you back $10-$15, treating around 50 liters. Their shelf life is pretty good too, often several years if stored properly. No maintenance here, just use and dispose of the packaging.
Gravity filters have a higher upfront cost… say $80 to $150 for a good system. The filter cartridge itself is the main consumable. These can typically treat anywhere from 1,000 to 5,000 liters, sometimes more, depending on water quality. Replacement cartridges might run $30-$50.
Maintenance for filters means:
- Occasional backflushing to clear pores.
- Protecting from freezing.
- Storing dry when not in use for long periods.
Over the long haul, if you treat a lot of water, a gravity filter might be more economical per liter. But for occasional use or emergencies, tablets are hard to beat for initial outlay and simplicity.