If your water runs out on a long hill day, UK health bodies advise against drinking untreated water, so a stream refill needs treating, and a filter does it at the stream.
For a soft bottle to fill at the stream and sip through, start with the LifeStraw Peak Series Collapsible Squeeze Bottle 1L.
LifeStraw lists bacteria and parasites as removed, and states that it does not remove viruses.
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The three, by how you carry and drink:
- For a soft 1 litre bottle to squeeze or sip from, choose the LifeStraw Peak Series Collapsible Squeeze Bottle 1L, with a 0.2 micron membrane.
- For a pouch you fill and squeeze, choose the Sawyer Squeeze, which Sawyer rates to 0.1 micron absolute.
- For a straw that also screws onto a bottle, choose the LifeStraw Peak Series Solo, which has a 0.2 micron membrane.
| Your day out | What to carry |
|---|---|
| You want a soft bottle to fill at the stream, with a squeeze or straw option | LifeStraw Peak Series Collapsible Squeeze Bottle 1L |
| You want a filter that screws onto a pouch or a standard bottle thread | Sawyer Squeeze |
| You want a straw that also fits a standard 28 mm bottle | LifeStraw Peak Series Solo |
LifeStraw Peak Series Collapsible Squeeze Bottle 1L
You want a soft bottle to fill at the stream, with a squeeze or straw option
LifeStraw Peak Series Collapsible Squeeze Bottle 1L Soft 1 L bottle with a 0.2 micron filterUse as a bottle, a squeeze system or a straw Read the full specification on AmazonLifeStraw says the filter removes 99.999999% of bacteria, 99.999% of parasites and 99.999% of microplastics, plus silt, sand and cloudiness. The Amazon listing names E. coli, Salmonella, Giardia and Cryptosporidium.
LifeStraw says the filter lasts up to 2,000 litres and stops the flow when it needs replacing.
LifeStraw describes three uses: drink from the bottle, squeeze water through it into cooking containers or other drinkware, or use it as a straw. The filter can be backflushed, and the listing includes a backwash syringe.
Best for: a walker who wants one soft bottle to fill and drink from.
Sawyer Squeeze
You want a filter that screws onto a pouch or a standard bottle thread
Sawyer Squeeze Water Filtration System 0.1 micron absolute filterScrews onto a collapsible pouch or a 28 mm bottle thread Read the full specification on AmazonSawyer rates the filter to 0.1 micron absolute. It states that the filter removes 99.99999% of bacteria, including salmonella, cholera, leptospirosis and E. coli, and 99.9999% of protozoa such as giardia and cryptosporidium.
You fill the pouch at a fresh water source, screw the filter on, and drink from the filter or squeeze the water into a bottle.
Sawyer lists collapsible pouches, including a 32 oz size, and says the filter also fits standard bottles with 28 mm threads.
Sawyer gives the filter alone as 3 ounces, about 85 g, and backs it with a lifetime limited warranty.
Its FAQ says backwashing may be needed only every 1,000 gallons with relatively clear water, but every 10 gallons with extremely turbid or muddy water.
Best for: a walker who wants to fill a pouch and pour the water into a bottle they already carry.
LifeStraw Peak Series Solo
You want a straw that also fits a standard 28 mm bottle
LifeStraw Peak Series Solo Personal Water Filter 0.2 micron membrane, 48.2 gWorks as a straw or screws onto a 28 mm bottle Read the full specification on AmazonLifeStraw says the Solo’s 0.2 micron membrane removes 99.999999% of bacteria and 99.999% of parasites, including Giardia and Cryptosporidium. It also removes 99.999% of microplastics, silt and sand.
LifeStraw lists the Solo at 48.2 g, with a filter life of up to 2,000 litres and a flow of 3 litres a minute.
It screws onto most standard 28 mm bottles and can also be used directly as a straw for lakes and streams. No bottle comes with it. When the filter reaches the end of its life, water no longer flows through.
LifeStraw’s FAQ says the Solo does not remove viruses. A backwash syringe is included for cleaning.
Best for: a walker who already carries a bottle and wants a filter to fit it.
What each filter removes
LifeStraw says in plain words that neither of its filters removes viruses.
| Filter | Bacteria and parasites | Viruses |
|---|---|---|
| LifeStraw Peak Squeeze Bottle | Bacteria 99.999999%, parasites 99.999% | Not removed, says LifeStraw |
| Sawyer Squeeze | Bacteria 99.99999%, protozoa 99.9999% | No claim on its product page or FAQ |
| LifeStraw Peak Solo | Bacteria 99.999999%, parasites 99.999% | Not removed, says LifeStraw |
Sawyer and the LifeStraw listings name giardia and cryptosporidium among the organisms.
TravelHealthPro is the UK national travel health service. It says a filter size from 0.2 to 1.0 micron can remove dirt and parasites, if the filter works correctly. That advice is written for travellers abroad.
Why a stream below farm animals needs filtering
The UK Health Security Agency says cryptosporidium may contaminate lakes, streams and rivers, and its advice is: do not drink untreated water.
UKHSA says cryptosporidium affects people and some animals, particularly farm animals. It can be found in the faeces of infected humans and animals. It says cryptosporidium in manure can contaminate fields and rivers.
Public Health Wales says cryptosporidium can affect people, livestock, wild animals and pets, and is found in lakes, streams and rivers. It gives the same advice: do not drink untreated water.
The NHS, the UK’s public health service, says you can get giardiasis from drinking water contaminated by the poo of infected people or animals.
Where to fill
Mountaineering Scotland, writing about the Scottish hills, says water above human habitation is generally safe to drink. You still have to think about where it comes from.
It says to take water from a flowing stream rather than still water. Its other points:
- Collect from upstream of all habitation and camping sites.
- Avoid water that is obviously muddied or where there is a lot of livestock.
- Avoid untreated water from farmland with intensive livestock around.
- Avoid water that looks stagnant, discoloured or oily.
Squeeze bottle, straw or pouch
- Squeeze bottle: the LifeStraw Peak Series bottle is a collapsible 1 litre bottle that you fill, drink from or squeeze into other containers.
- Straw: the LifeStraw Peak Series Solo works directly as a straw, so you drink at the water. On a 28 mm bottle it filters from a bottle you filled earlier.
- Pouch: the Sawyer Squeeze screws onto a pouch you fill at the stream. You drink from the filter or squeeze the water into a bottle.
A frozen filter
Sawyer says its filters withstand temperatures from 0 to 60°C (32 to 140°F).
In freezing temperatures it recommends keeping the filter in your pocket or close to your person, and replacing a filter you suspect has been frozen.
Tablets and boiling
In its advice for travellers, TravelHealthPro says chlorine tablets do not always destroy cryptosporidium and giardia. It adds that cold water can weaken chemical treatments.
It says chlorine dioxide is more effective against parasites.
A BMC panel contributor suggests carrying purification tablets for streams on the Welsh 3000s. Mountaineering Scotland, writing for the Scottish hills, says boil for one minute at a rolling boil, which does not remove sediment.
Water on Yr Wyddfa
There is no tap at the summit of Yr Wyddfa, and the Eryri National Park Authority says to carry at least 1.5 litres per person.
The Authority, the public body that runs the park, says its designated water taps provide fresh Welsh water that is safe to drink. It also asks walkers to fill the bottle to the brim before setting off.
The rest of your kit is on the what to pack list, and your day rucksack decides how you carry the water.
We compile and explain public route and safety information. We guide nobody and sell nothing on the hill.
Before you drink from a stream
- Fill the bottle to the brim at the start, with at least 1.5 litres on Yr Wyddfa.
- If you run short, choose running water away from farm animals, as Mountaineering Scotland advises for the Scottish hills.
- Filter it, and remember that LifeStraw says neither of its filters removes viruses.
- In frost, keep a Sawyer filter close to your body, as Sawyer advises.
If your water may not last the whole day, carry the LifeStraw Peak Series squeeze bottle.
