A water filter or purifier offers peace of mind and guaranteed safe drinking water at a hut, alpine tarn or stream.
How to filter
Always check – if possible – what’s in the water upstream to avoid contamination. Giardia slowly sinks, so draw your water where the flow is slow-moving, away from the bank. Avoid muddy water as it can contain bacteria stirred up from the streambed and will also clog filters.
The usual flow (or purification) rate is one to two litres per minute. It’s important to keep filters clean and free of sediment to ensure the flow rate remains high.
Water filters and purifiers are designed to protect users from water-borne illnesses like giardia, campylobacter, salmonella and E. coli.
To ensure the long life of your filter, clean it regularly. This is usually done by rinsing or backwashing and can be accomplished in the field as well as at home.
What purifiers do
Purifiers kill the much smaller viral and bacterial organisms. UV light is the most common and effective form of purification. It is important to follow instructions precisely to ensure the purification process is adequate.
The full system
Some systems use both a filter and purifier. The filter removes organisms down to 0.2 or 0.1 micron and the purifier deals with anything smaller. Unless the removal of organisms is at least 99.9%, there is a risk of infection.
When to use
If you’re carrying a filter or purifier, you should use it every time you collect water for drinking, even in the remote backcountry where the risk of contracting a water-borne illness might seem small. The risk increases in more popular areas, where people might go to the toilet near waterways or where animals are grazed. In urban environments, a disaster like an earthquake can make a water filter or purifier a life-saver. Because animals often fall into hut water tanks where they drown, it’s wise to filter or purify (or at least boil) any water you drink.
What filters do
Filters are the first line of defence against larger-than-a-virus protozoa and cryptosporidia such as Giardia Lamblia and parvum. Filters remove sediment and organisms down to 0.4-0.1 microns.
MSR Guardian Gravity Purifier $499.99
High-volume water purifier using hollow fibre and activated carbon to remove viruses, protozoa, bacteria and microplastics, and reduce foul tastes. Integrated purge valve flushes system clean. Flow rate 0.5-litre/min Cartridge life 3000+litres Weight 532g. e.ampro.co.nz
SteriPEN Adventurer Opti $269.95
Compact handheld water purifier using ultraviolet light to kill up to 99.9999% of all waterborne bacteria and 99.99% of all viruses. Single-button operation. Uses two CR123A batteries. Purifier life 8000-litres Output 1-litre/90sec Weight 110g. www.outfitters.net.nz
MSR MiniWorks EX $229.99
Field maintainable microfilter, removes unpleasant tastes and odours caused by organic compounds as well as 99.9999% of bacteria and 99.9% of protozoa. Flow rate 1-litre/min Cartridge life 2000+litres Weight 456g. e.ampro.co.nz
SteriPEN Classic 3 $199.95
Patented handheld water purifier uses ultraviolet light to kill up to 99.9999% of all waterborne bacteria and 99.99% of all viruses. Pre-filter included. Requires 4xAA batteries. Purifier life 8000-litres Output 1-litre/90sec Weight 225g. www.outfitters.net.nz
MSR TrailShot MicroFilter $129.99
Drink directly from the source or refill drink bottles, quick-deploy design, squeezing action pumps water through filter, removes 99.9999% of bacteria and 99.9% of protozoa. Flow rate 1-litre+/min Cartridge life 2000-litres Weight 153g. e.ampro.co.nz
Sawyer Squeeze Filter $119.95
A 0.1 micron filter removes 99.99999% of all bacteria, 99.9999% of all protozoa and other particles. Field-maintainable, includes two re-usuable one-litre squeezable pouches, inline adapter, syringe, and a mesh bag/tubing for gravity system. Flow rate 2.5-litre/min Filter life 378,000-litres Weight 65g. www.alpineandleisure.co.nz
Platypus QuickDraw Microfilter with 1L bottle $99.99
Taste-free reservoir has a wide mouth for rapid filling. Easy to clean, and with a 0.2 micron hollow fiber cartridge to remove 99.9999% of bacteria and 99.9% of protozoa. Flow rate Up to 3-litre/min Cartridge life 1000-litres Weight 101g. e.ampro.co.nz
Sawyer Mini Filter $79.95
A 0.1 micron filter removes 99.99999% of all bacteria, 99.9999% of all protozoa and other particles. Field-maintainable, includes 470ml drinking pouch, straw to drink directly from a water source. Connects to hydration reservoir and disposable water bottles. Flow rate 1.5 -litre/min Filter life 378,000-litres Weight 38g. www.alpineandleisure.co.nz
Water to go 500ml/750ml $64.99/$89.99
Three-in-one filter removes up to 99.9999% of bacteria and viruses, removes foul tastes and odours as you drink, BPA-free bottle, 500ml and 750ml bottle sizes. Cartridge life 130-, 200-litres Weight 98, 138g. www.watertogo.co.nz