Hollow-fibre squeeze filter
Plus chlorine tablets as the backup.
What to look for: Hollow-fibre squeeze filter, plus chlorine dioxide tablets
Handles the bacteria and protozoa that matter on a Nepali trail, works from a teahouse tap, and saves buying bottled water — which climbs steeply with altitude and has been reported as high as several dollars a litre at the top lodges.
A UV pen works too; trekkers report using one for years, often alongside a filter for redundancy. If you use chemical tablets, note that chlorine dioxide needs several hours of contact time, not minutes.