Hello pretty much as the title says, what is the best for use in Nepal and Indian Himals

Thanks

Halides will only do the same as boiling (ie kill biologicals) but nothing against chemical contaminants – filters can remove chemicals but not biologicals.
Personally I'd filter the water and boil immediately before use unless there's some new gizmo that does chemical/bilogical decon in a single action…….

what he says. Depends where you are getting your water from though – a 'fresh' mountain stream shouldnt be a great problem for anything chemical.