Hydration is not a side issue at altitude. Fast breathing in dry, cold air loses far more water than you would expect, and dehydration mimics and worsens the symptoms of altitude sickness. Three to four litres a day is the working target above 3,000 m, and more on a hard pass day.
The question is how to make that water safe. Stream and tap water on Nepal's trails carries bacteria, viruses, and protozoa including giardia, and a week of giardiasis at 4,000 m will end a trek. There are five realistic options, and they are not equally good.
The Five Options Compared
| Method | Kills | Cost on a 12-day trek | Weight | Verdict |
|---|---|---|---|---|
| Chlorine dioxide tablets or drops | Bacteria, viruses, protozoa including giardia | USD 10–20 | Negligible | Best all-round choice. Wait 30 minutes, 4 hours for cryptosporidium. |
| Squeeze or pump filter (0.1 micron) | Bacteria and protozoa, not viruses | USD 30–100 one-off | 60–300 g | Fast and tasteless. Best paired with tablets, and must not freeze. |
| UV steriliser pen | Bacteria, viruses, protozoa | USD 80–130 one-off | 150–200 g | Excellent but battery-dependent, and cold drains batteries fast. |
| Boiled water from the lodge | Everything | NPR 100–300 per litre | None | Reliable, but costs money and burns kerosene or firewood. |
| Bottled mineral water | Everything | NPR 100–400 per bottle | None carried | Avoid. Discouraged across conservation areas, banned in parts of the Khumbu. |
Our recommendation for most trekkers is simple: a one-litre wide-mouth bottle, a two-litre bladder, and chlorine dioxide tablets, with a filter as a luxury if you dislike the faint taste. Total weight under 200 g, total cost under USD 20, and nothing to break at 5,000 m.
Why Bottled Water Is the Wrong Answer
It is the easiest option and the worst one. Every bottle is flown or carried to altitude and then has to come back down as rubbish, which frequently does not happen — it is burned behind lodges or buried. The Khumbu Pasang Lhamu Rural Municipality banned the sale of single-use plastic water bottles above Lukla in 2020 for exactly this reason, and refill stations operate in several villages.
There is a cost argument too. Bottled water on a two-week Everest trek can run to USD 80 or more, against USD 15 for tablets. You are paying a premium for a product that makes the trail worse.
How to Actually Do It Each Day
- Fill both bottles at the lodge tap each morning and dose them with tablets before breakfast. By the time you leave, they are ready.
- Refill at lodges during the day rather than from streams where you can. Lodge water is piped from a spring and generally cleaner at source.
- Drink steadily through the day — half a litre an hour of walking — rather than a litre at lunch.
- At the lodge in the evening, fill a wide-mouth bottle with boiled water and put it in your sleeping bag. It is both a hot water bottle and your breakfast litre.
- Keep filters and bottles out of the cold overnight. A frozen filter cartridge is a broken filter cartridge.
Use treated water for brushing your teeth too. It is a small discipline that prevents a disproportionate number of upset stomachs.
Signs You Are Not Drinking Enough
At altitude, dehydration and mild altitude sickness produce almost the same symptoms, which is why guides ask about your fluid intake before anything else.
- Dark urine — the most reliable field check. Aim for pale straw.
- Headache that eases after half a litre and a rest.
- Cracked lips, dry cough, and a raw throat.
- Unusual fatigue on a day that should have felt easy.
If the headache does not respond to fluid and a simple painkiller, treat it as altitude rather than dehydration and tell your guide. Our altitude guide sets out what happens next.
Hot Drinks, Electrolytes, and What Not to Drink
Tea counts toward your intake, and lodges pour a lot of it — masala tea, black tea, and the lemon ginger honey that every trekker ends up addicted to by day four. Butter tea in Tibetan-Buddhist villages is salty rather than sweet and worth trying once for the experience and once for the calories.
Electrolyte or rehydration salts are genuinely useful on hard days and essential if you have had any stomach trouble — plain water alone does not replace what you lose. Carry a few sachets.
What to avoid: alcohol above 3,000 m, because it dehydrates and suppresses night-time breathing; a lot of coffee, for the same dehydrating reason; and untreated stream water, however clear and however high. There is usually a yak pasture upstream.
Refill Points on the Main Trails
Three regions have gone furthest in replacing bottled water with refills, and knowing where the stations are makes the habit easy rather than worthy.
- The Khumbu — safe drinking water stations operate in Lukla, Namche Bazaar, and several villages up to Dingboche, selling boiled and filtered water by the litre at a fraction of the bottled price. Single-use plastic bottles have been banned above Lukla since 2020.
- The Annapurna region — stations run by the conservation area authority appear in Chhomrong, Ghorepani, Manang, and along the Jomsom road, and lodges throughout the area sell boiled water.
- Langtang — refills are available through most lodges from Syabrubesi to Kyanjin Gompa, though dedicated stations are fewer.
On remote and restricted routes — Upper Dolpo, Kanchenjunga, Makalu — there are no stations at all, and some nights are camping. Carry tablets and a filter on those trips and treat every litre yourself; our camping crews boil water for the group as well.
