I’ve used water from all sorts of natural sources while hiking in New Zealand without any issues. And then one day I saw a dead rat floating in a water tank at a hut and decided it was no longer worth the risk. I’ve carried a water filter ever since. Even in remote wilderness, natural water or tank water isn’t guaranteed safe. Here’s why untreated water can be dangerous:

• Giardia and cryptosporidium – common in rivers and lakes; spread by humans and animals.

• Bacteria like E. coli – often from animal faeces upstream.

• Viruses – more common in warmer climates or heavily used catchments.

• Farm runoff – fertilisers, pesticides, and animal waste can leach into waterways.

• Animal carcasses and vegetation – a dead animal upstream can foul an entire creek.

• Hut and campsite water tanks – easily contaminated by bird droppings, insects, dead animals, or poorly maintained gutters.

The bottom line: you can’t tell if water is safe just by looking at it.

How to Choose the Safest Natural Water Sources

Not all water is equal in the outdoors. Follow these guidelines before you filter or treat it:

1. Collect water higher up – Where you know there’s no farming and you’re closer to the source (snow melt).

2. Pick fast-flowing water – Moving streams are safer than stagnant tarns, ponds, or swamps.

3. Avoid farmland and huts – Don’t fill bottles downstream of stock paddocks or popular campsites.

4. Look for clarity – Clear water clogs filters less and indicates lower sediment load.

5. Check tributaries – Small side-streams often run cleaner than main rivers.

6. Rainwater tanks – Always treat hut and campsite water.

When it comes to the best ways to purify water on a hike, there are four main methods that trampers, hunters, and campers rely on:

1. Boiling Water

• How: Bring water to a rolling boil for 1-3 minutes.

• Pros: Kills all bacteria, protozoa, and viruses. Foolproof.

• Cons: Time and fuel intensive. Doesn’t improve taste or remove dirt. And you have to wait for it to cool down.

2. Portable Water Filters

These are tend to be small, lightweight filters that attach to a hydration bladder or drink bottle so you can simply fill up at a stream, river, or tarn and drink the water through the filter. Some drink bottles come with a built-in water filter.

• How: Pump, squeeze, gravity, or straw filters remove pathogens and sediment.

• Pros: Fast, effective, improves taste. You can drink water straight from a dirty puddle in some cases.

• Cons: Filters clog in silty water. Most don’t remove viruses.

3. Chemical Water Treatment (Chlorine Dioxide Tablets)

• How: Drop in tablets, wait 30–60 minutes.

• Pros: Lightweight, effective against viruses, easy to carry.

• Cons: Chemical taste, slower in cold or dirty water.

4. UV Light Purifiers

• How: Insert UV wand into bottle, stir for 60–90 seconds.

• Pros: Fast, kills bacteria, protozoa, and viruses.

• Cons: Expensive, needs batteries, doesn’t work in cloudy water, no sediment removal.

What If Only Dirty Water Is Available?

Sometimes, despite good planning, your filter breaks, you lose your tablets, or the only water source is stagnant and dirty. Here’s how to make the best of a bad situation:

1. Settle and pour off – Let water sit until sediment sinks, then decant the clearer top layer.

2. Pre-filter with cloth – Use a t-shirt, bandana, or moss-packed bottle to strain debris.

3. Boil if possible – Even muddy water is safer boiled than clear but untreated water.

4. Use sunlight (SODIS method) – Fill clear bottles, leave in direct sun for 6+ hours. UV rays kill many pathogens.

5. Hydrate when necessary – In survival situations, dehydration is more dangerous in the short term than giardia. Drink the best-prepared water you can.

⚠️ These are last-resort methods. Always carry at least two treatment systems so you don’t rely on improvisation.

Is river or stream water safe to drink without treatment?

Maybe, but is it worth the risk? Even if water looks crystal clear, it can carry giardia, cryptosporidium, or E. coli. These microorganisms are invisible to the naked eye and can make you very sick for weeks. In New Zealand and Australia, parasites are common in high-country streams due to animal and human contamination. Always treat water before drinking – either by boiling, filtering, or chemical/UV treatment.

Do hut water tanks have safe drinking water?

Not necessarily. Hut and campsite water tanks collect rainwater, but gutters often harbour bird droppings, leaves, and insects. Once inside the tank, bacteria and parasites can thrive. DOC and park authorities often recommend boiling or filtering hut water before use. If you’re short on fuel, a filter system like the Ninety9 Pure Hydration Bladder is the easiest and quickest way to make tank water safe.

What’s the fastest way to purify water on a hike?

A portable water filter or straw is the quickest option, as it lets you drink almost immediately. Straw-style filters let you sip directly from streams, while bladder systems filter as you drink. They’re also compact and lightweight for bringing with you on a hike.

What’s the lightest water treatment method for multi-day trips?

Chlorine dioxide tablets are the most lightweight and compact method – a strip of tablets can treat several litres of water and weighs almost nothing. They’re also effective against viruses, which most filters miss. The downside is the wait time (30–60 minutes) and the slight chemical taste. Many trampers carry tablets as a backup to a filter system, so they’re covered if gear fails.

Can I rely only on boiling to make water safe?

Yes, boiling is the most reliable purification method – it kills all bacteria, protozoa, and viruses. However, it uses fuel, takes time, and won’t remove sediment or improve taste. On short trips with a gas cooker, boiling alone is fine. On longer missions, a filter plus tablets is more efficient because you won’t burn through all your fuel just treating water.

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