Grayl takes a different approach to water purification — press down on the outer bottle to force water through an internal purifier cartridge. Fill, press (8–10 seconds), drink. No pumping, no squeezing, no waiting.
The key differentiator: Grayl purifiers remove viruses as well as bacteria, protozoa, chemicals, and microplastics. Standard hollow fibre filters don't remove viruses. For international travel in regions where viral water contamination is a concern, Grayl's purifier is the more comprehensive option.
For NZ tramping: Giardia (a protozoan) is the main backcountry water risk — removed by all filters. Viral contamination is not the primary NZ concern. If you use your purifier both in NZ and internationally, Grayl covers both use cases in one unit.
The GeoPress 710ml is the practical choice for most users — larger capacity, fewer fill cycles, robust build for backcountry use. The UltraPress 500ml is lighter and more compact, better suited to weight-conscious trampers and travel where smaller capacity is sufficient.
Frequently Asked Questions
Does Grayl remove viruses, and do I need that for NZ?
Yes, Grayl removes viruses — hollow fibre filters don't. For standard NZ backcountry tramping, Giardia is the main concern and a hollow fibre filter covers it. Grayl becomes the better choice if you also travel internationally to regions where viral contamination is more likely, or if you want maximum purification in a single simple unit regardless of conditions.
How long does a Grayl cartridge last?
GeoPress cartridge: rated to 250 litres (approximately 350 presses). UltraPress: 150 litres. For most trampers and travellers drinking 2–3 litres per day, a GeoPress cartridge covers months of use. Press resistance increases noticeably as the cartridge approaches end of life. Replacement cartridges available from Dwights.
GeoPress vs UltraPress — which should I choose?
GeoPress (710ml) for backcountry tramping — more capacity means fewer fill cycles from streams, and the build is more robust. UltraPress (500ml) for weight-conscious trampers or travel use where you're filling from taps and café water rather than streams. If in doubt, GeoPress.