A note before the comparison, and it governs everything below. This page reports what each manufacturer declares about its own product: the pore size it publishes, the litres it claims, the format it sells. It does not say that any filter makes any water safe to drink, and it does not say the opposite either. Whether a given source can be used is a matter for the maker’s own instructions and for the authorities responsible for that water, and it is decided at the source, not on a comparison page.
With that stated plainly, three published figures separate these filters, and two important ones are missing from every listing in the family.
Pore size, as each maker publishes it
Micron figures on this shelf fall into three bands, and the band is more informative than the decimal place.
0.01 micron is declared by Purewell, which states it twice — as 0.01 μm in its title and as a filtration accuracy of 0.01 micrometre in its bullets — and by SURVIVO, which also states it twice, once as 0.01 micrometre and once as 0.01 µm. A figure printed twice in two forms is a maker committing to it rather than dropping it into a title.
0.1 micron is declared by Waterdrop, as a 0.1 µm ultrafiltration membrane, and by Gipfelrein, as a pore size of 0.1 µm.
0.2 micron is declared by BACHGOLD, as a filtration accuracy of up to 0.2 µm.
And two of these publish no micron figure at all. The GRAYL publishes a replaceable press-through cartridge and does not name the media inside it. The RIF. names its medium — KDF-55, which the maker describes as removing heavy metals and chlorine — and publishes no pore size. Both are telling you something real and neither is telling you the same thing as the others.
Cartridge life, and the running cost behind it
Every filter here is a consumable with a body attached, and the stated litres are how the maker expects that consumable to be budgeted.
Waterdrop states up to 5300 litres. SURVIVO states up to 4000, in its title and again in its bullets, and RIF. states 4000 in its title. BACHGOLD and Purewell both state 1500. Gipfelrein states up to 4000 for its hollow-fibre membrane.
The GRAYL states 250 litres for its replaceable cartridge, which is an order of magnitude below the rest and is not a defect: it is a different product design, in which the cartridge is expected to be replaced as a routine cost rather than to last the life of the bottle. Read it as a subscription rather than as a shortfall, and price the replacements before ordering.
This is where the real choice sits, because the filter you use every day is the one that suits how you actually drink.
A press bottle treats a fixed volume at a time. BACHGOLD is an all-in-one press-through bottle of 500 ml, stated to need no additional components. GRAYL treats 710 ml at a time — fill, press, drink, with no pumping, batteries or chemicals. OUTDOOR-FRIENDS, elsewhere on this site, is a press bottle with a magnetic lid whose volume is never published.
A straw is the lightest thing to carry and the most awkward to drink from at a stream. Purewell is a straw with a carabiner, stated to be drawn through at the source or fitted into a water bottle, and it names all four of its stages: a hollow-fibre ultrafiltration membrane, PP cotton, coconut-shell activated carbon and an adsorption ball. That is more detail on the element than anything else on this page gives.
A gravity set does the work while you do something else. Waterdrop supplies a straw with a gravity water bag, states that both ends come apart, and states that it works with bags or bottles. For a camp where a bag can be hung on a branch and left to run, that is a different daily rhythm from squeezing a bottle.
An in-line or bottle-mounted filter joins kit you already own. SURVIVO states a standardised thread for commercially available PET bottles and states that it connects to water bags and drinking systems, which makes it the natural pairing for a hydration reservoir. RIF. states a universal adapter said to fit almost all common bottle sizes. Neither publishes a thread size in millimetres, so “universal” is the maker’s word rather than a measurement you can check.
A filter with its own bottle is the compact set. Gipfelrein supplies a screw-on filter with a foldable 0.5 litre bottle, a lanyard and a carabiner.
The two figures nobody publishes
Not one filter on this site publishes a flow rate, and not one publishes a weight.
Flow rate is what separates a filter you top up from a filter you resent. A straw drawn through a loading membrane and a gravity bag hung on a branch are very different experiences of the same stated pore size, and no listing here quantifies the difference.
Weight matters for the same reason it matters everywhere else on this site: a press bottle with a cartridge inside it is a heavier object than a straw, and none of these listings will tell you by how much. If it is going in a pack, weigh it when it arrives.
Backflushing and maintenance
The one maintenance detail published here comes from Waterdrop, which states that its filter is backflushed without a syringe. Every hollow-fibre element slows as it loads, and how it is cleared is the difference between a filter that lasts its stated litres and one that gets left at home. Where a listing does not describe the procedure, the instructions in the box are the place to look before the first trip rather than during it.
Choosing between them
If a bag can be hung at camp, the Waterdrop set states more litres per cartridge than anything else on this page, and adds a straw for use at the source. If a straw carried as a backup is the plan, Purewell names every stage of its element. If you already run a hydration reservoir, SURVIVO goes into the line. If you already carry a bottle you like, RIF. adapts to it. If one small bottle refilled at the stream is the whole water plan, BACHGOLD or Gipfelrein do that in one object. And if you would rather treat a fixed volume and replace the cartridge on a schedule, the GRAYL is built around that habit.
Whichever you choose, the notice in the box is the document that governs its use, and local guidance governs the water.
