Save on stove fuel by packing a filter or purifier to ensure the water you drink is safe.

Save time and lighten your load

Filters and purifiers can reduce pack weight by allowing water to be sourced on the go, rather than carrying extra litres (1l weighs 1kg) from home. These units also save time as water needn’t be boiled to make it safe to drink.

Water-borne hazards

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

When to use

If you’re carrying a filter or purifier, it should be used every time water is collected 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 bird droppings and animals often end up in hut water tanks, it’s wise to treat (or at least boil) all drinking water.

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 a filter, clean it regularly. This is usually done by rinsing and can be accomplished in the field as well as at home.

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Platypus QuickDraw Microfilter with 1L bottle $134.99

Fill and squeeze this microfilter for safe hydration in the hills. Its RF-welded taste-free reservoir has a wide mouth for rapid filling. 0.2 micron hollow fibre filter removes 99.9999% of bacteria and 99.9% of protozoa. Flow rate Up to 3l/min Filter life 1000l Weight 101g. www.ampro.co.nz

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MSR TrailShot MicroFilter $169.99

Drink directly from the source or refill drink bottles, quick-deploy design, squeezing action pumps water through filter to remove 99.9999% of bacteria and 99.9% of protozoa. Flow rate 1l+/min Filter life 2000l Weight 153g. www.ampro.co.nz

MSR MiniWorks EX‭ $‬299.99

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

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MSR Guardian Purifier $949.99

This purifier offers advanced technology for global travellers, backcountry users and emergency kits. Full viral protection when travelling in developing nations and popular wilderness areas. Advanced hollow fibre filter offers reliable purification of even filthy water conditions. Long-lasting performance, self-cleaning. Flow rate 2.5l/min Filter life 10,000l+ Weight 490g. www.ampro.co.nz

Kea Awa $50

Featuring a nano-fibre filter that purifies fresh water. Removes 99.9999% of bacteria, 99.9% of protozoan cysts and 99.99% of viruses and some chemicals and heavy metals. Drink directly from the source or a drink bottle with the extension straw. Self-cleaning, five-year shelf life. Includes a carry bag. Filter life 300l+ Weight 45g. www.keaoutdoors.co.nz

Lifesaver Wayfarer $259.99

A pump-style water purifier for hikers. It removes up to 99.9999% of bacteria, 99.999% of viruses and 99.99% of protozoa. Water is pumped directly from the source through a two stage filtration system into a drink bottle. Failsafe Technology prevents water passing through once the filter membrane becomes blocked. Purifier life 5000-litres Output 1.4-litre/min Weight 323g. www.plg.com.au

Sawyer Squeeze $125

A lightweight filter rated to 0.1 micron to remove 99.99999% of all bacteria, E. coli and protozoa. Filter is back-washable and comes with two squeeze pouches, gravity system, inline adapters or screws straight onto a bottle. Lifetime warranty. Flow rate 3l/min  Filter life 400,000-litres Weight 85g. www.alpineandleisure.co.nz