Drinking water on a Nepal trek: treating, buying and refilling

Do not drink untreated water on a Nepal trek, however clear it looks. Boiling for one full minute kills the germs that matter, even at 4,900 metres, where water boils at about 83 degrees C. A filter removes bacteria and parasites but not always viruses. Bottled water can cost NPR 200 to 400 a litre above Chhomrong, and glass and plastic bottles are reported banned at Annapurna Base Camp, so carry a refillable bottle and a backup treatment.

Why is water the main health risk you can control on a trek?

Stomach illness can end a trek as surely as altitude, and you can reduce it with a few habits. In one older study, a 2001 survey of 26 water sources from Pokhara to Muktinath found total coliform bacteria in 94 percent of samples and E. coli in 72 percent. Most of that water came from springs or streams through plastic pipes. The study is old and only a conference abstract, and we found nothing newer for this route, but it shows that a clear mountain tap proves nothing.

The germs to worry about are bacteria, viruses and parasites such as Giardia and Cryptosporidium. CDC also recommends the hepatitis A vaccine for unvaccinated travellers to Nepal and typhoid vaccine for most travellers. See a travel clinic before you leave, because vaccines work alongside safe water, and they do not replace it.

Which treatment should you choose?

Each method has a weakness, so the best kit pairs two. This table summarises the CDC Yellow Book chapter on water disinfection.

Method	Works against	Weak point	Best for
Boiling, 1 full minute	All germs	Needs fuel, so lodges charge for it	Evening and morning refills
Chlorine dioxide	All germs, including Cryptosporidium	Tablets or drops need several hours	Overnight treatment
Chlorine or iodine	Bacteria, viruses, Giardia with longer contact	Poor against Cryptosporidium	Cheap backup
Microfilter, under 1 micron	Bacteria, Giardia, Cryptosporidium	Does not reliably remove viruses	Quick refills, with chlorine added
UV pen	All germs	Needs clear water and battery power	One litre at a time

A good simple kit is a filter plus chlorine dioxide tablets, or a UV pen plus tablets. Iodine has limits of its own. CDC says to use it for a few weeks at most, and to avoid it if you are pregnant, have unstable thyroid disease or have an iodine allergy.

Do you need to boil water longer at altitude?

Not according to the CDC traveller chapter. It says germs die within seconds at boiling point, and asks for a full minute as a margin. At about 4,900 metres water boils near 83 degrees C, which is still well above the 60 to 70 degrees C range that kills gut germs. Some guides still say to boil for three minutes up high. Extra boiling does no harm, but it burns fuel that was carried a long way.

What about cloudy glacier water?

Cloudy water needs extra care. Silt can shield germs from UV light, weaken chemical treatment and clog filters. Letting it settle first helps. CDC's food and water chapter adds that cloudy or discoloured water may contain chemicals that boiling and disinfection cannot remove. If you have a choice, take clear water from a lodge tap or a spring, and treat it.

Can you buy or refill water on the trail?

You can buy bottled water on most routes, though the price climbs with altitude. Our Annapurna Base Camp cost guide puts it at NPR 200 to 400 a litre above Chhomrong. CDC treats factory-sealed bottles as generally safe, so check that the seal is intact.

Plastic is the problem. In September 2024 a Nepali tourism site reported that the Annapurna Conservation Area Project (ACAP) had banned glass and plastic bottles from Annapurna Base Camp, and had asked visitors not to bring them to Mardi Himal or Tara Hilltop. We did not find the original ACAP notice, and we cannot say how strictly it is enforced. In 2025 the National Trust for Nature Conservation also asked trekkers to carry reusable bottles. Plan on your Annapurna Base Camp trek without bottled water.

Lodges will usually sell boiled water by the litre or fill a flask, and many treks have refill points. Agency websites describe Safe Drinking Water Stations in villages such as Chame and Manang, with prices from NPR 25 to 100 a litre. We could not confirm these through ACAP or any newspaper, and some may be closed. Ask your guide, and keep your own treatment as the plan you rely on.

How do cold nights change your water plan?

Cold can quietly break your kit, and the risk grows above about 3,500 metres.

• Protect hollow-fibre filters. One maker's guidance says there is no sure way to tell whether a filter has been damaged by freezing. It advises replacing any filter you think has frozen, and keeping it in your sleeping bag at night.
• Keep UV batteries warm. Cold drains batteries, so carry the pen inside your jacket.
• Stop your bottle freezing. Take hot boiled water to bed in a sealed bottle. It warms the sleeping bag and gives you liquid water in the morning.
• Use wide-mouth bottles. Narrow necks and hose bite valves freeze first.
• Allow time for tablets. Chemical treatment works more slowly in cold water, so treat it the night before and follow the label.

How much water should you drink at altitude?

Drink enough that you are not thirsty and your urine stays pale. We found no official target in litres, and many trekkers aim for about 3 litres a day. More is not better. A summary of Wilderness Medical Society guidelines says forced overhydration does not prevent altitude illness and raises the risk of dangerously low blood sodium. It does say to stay hydrated, because dehydration symptoms can look like acute mountain sickness. The NHS also advises drinking enough to avoid dehydration.

So do not treat water as a cure. A headache that does not settle after drinking and rest may be altitude sickness, and our altitude sickness prevention guide explains what to do next.

What should you do if you get diarrhoea?

Replace fluids first, using sealed, boiled or treated water. The CDC chapter on traveller's diarrhoea says bacterial cases usually last 3 to 7 days without treatment, viral cases 2 to 3 days, and parasite infections can last weeks. Nepal is one of the best-known risk areas for Cyclospora, and risk in South Asia is much higher in the hot months before the monsoon.

• Rehydrate. For heavy fluid loss, mix oral rehydration salts in about 1 litre of treated water.
• Use loperamide carefully. Do not take it alone if you have a fever or blood in your stool.
• Ask your doctor about a standby antibiotic before you travel. CDC prefers azithromycin for fever or bloody diarrhoea, and notes that resistance limits fluoroquinolones in South Asia.
• Tell your guide. Weakness and vomiting up high can be altitude sickness, and our guides carry pulse oximeters to help them check.
• Get medical care for blood in the stool, a high fever, or symptoms that last more than a few days.

Wash your hands before eating, since your own hands can undo all your careful water treatment. If you use sanitiser, CDC says it should have at least 60% alcohol, and it works less well against Cryptosporidium. Pack your kit with our Nepal trekking packing list. For help with your route, contact us.

Frequently asked questions

Is the tea safe?

Yes, generally. CDC says drinks made with freshly boiled water, such as tea and coffee, are usually safe. Hot lemon or black tea also counts toward your daily fluid.

Can I brush my teeth with tap water?

CDC says tap water that may be unsafe should not be used for brushing teeth. Use your treated water, and keep your mouth closed in the shower.

Are filter bottles enough on their own?

Not always. Many filter bottles remove bacteria and parasites but not viruses. One maker says plainly that a 0.1-micron filter is too coarse for viruses. Check the label, and add chlorine or use boiled water if your filter does not cover viruses.

Is ice safe in Pokhara and Kathmandu?

Avoid it unless you are sure it was made with safe water. CDC notes that alcohol in a drink does not kill germs in the ice.