Water-borne illnesses can be contracted even when drinking from the most sublime alpine river. Using a water filter or purifier offers peace of mind and guaranteed safe drinking. 

Water-borne hazards

Water filters and purifiers are designed to protect users from water-borne illnesses like giardia, campylobacter, salmonella and E. coli. 

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 backcountry where the risk of contracting a water-borne illness might be 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 turn a water filter or purifier into a life-saver.  

Because animals often fall into hut water tanks, it’s wise to filter or purify (or at least boil) any water you drink. 

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. 

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. 

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.

Flow rates

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.

Cleaning

To ensure the long life of your filter, clean it regularly. This is usually done by rinsing and can be accomplished in the field as well as at home.

MSR Guardian Purifier $699.99

Offers full viral protection when travelling in developing nations and popular wilderness areas. Advanced hollow fibre filter purifies filthy water conditions. Self-cleaning, long-lasting performance. Flow rate 2.5l/min Cartridge life 10,000l+ Weight 490g. www.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 8000l Output 1l/90sec Weight 225g. www.outfitters.net.nz

LifeSaver Liberty Water Purifier Bottle $364.99

The only portable water purifier bottle and inline pump combined. Removes 99.999% of viruses, 99.9999% of bacteria, 99.99% of cysts, includes 400ml bottle, hose for drawing water from source, replaceable filter, activated carbon disc to reduce chemicals and heavy metals. Flow rate 1.2l/min Filter life 2000l Weight 425g.  www.plg.com.au

MSR TrailShot MicroFilter $129.99

Drink directly from the source or refill drink bottles, quick-deploy design, squeezing action pumps water through filter. Flow rate 1l+/min Cartridge life 2000l Weight 153g. www.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 8000l Output 1l/90sec Weight 110g. www.outfitters.net.nz

MSR MiniWorks EX $229.99

Easy-to-maintain microfilter, removes bacteria, protozoa and unpleasant tastes and odours caused by organic compounds. Field maintainable. Flow rate 1l/min Cartridge life 2000l+ Weight 456g. www.ampro.co.nz

Platypus QuickDraw Microfilter with 1L Bottle $99.99

Fill and squeeze for safe hydration. Taste-free reservoir with wide mouth for rapid filling and easy cleaning. 0.2 micron hollow fibre cartridge removes 99.9999% of bacteria and 99.9% of protozoa. Flow rate Up to 3l/min Cartridge life 1000l Weight 101g. www.ampro.co.nz

Aquatabs $14.99

Purification tablets that kill waterborne organisms like Giardia to make water safer for drinking, brushing teeth and food prep. www.ampro.co.nz