UV water purifiers

making it the fastest treatment method that does not change the flavour of the water. Clarity is a requirement: in cloudy water, the rays scatter and part of the volume remains untreated, so strain the water first. It also does not catch sand, chemicals and metals; for that, you need a filter. The whole device relies on batteries, which lose capacity in freezing conditions, so carry it close to your body and take a spare power source on longer trips. The glass tube is fragile, store it in a hard case and not at the bottom of a backpack.