3 to 5 Days
Assuming you’re in reasonable shape and in ideal conditions – that is, not in the heat or cold and not exerting, a human can probably live for about 3 to 5 days without any water.
In hot conditions with no water, dehydration can set in within an hour. Someone who is physically overexerted in the heat without replacing fluids can actually die in a period of several hours.
In severe heat, an adult can lose as much as 1.5 liters of water through sweat alone. The main risk without water in high heat is that your body temperature will continue to rise and you’ll suffer from heat stroke.¹
Enter Katadyn Products Inc. The Swiss Katadyn company is the world’s number one brand for individual water purification systems and products. Numerous international relief organizations and special army units rely on the products of Katadyn for survival and life saving.
As mentioned in the video, the Katadyn Vario Water Filter features a unique dual technology filtration system. In “Longer Life” mode (intended for turbid water sources) the ceramic disk is engaged to help protect the glassfiber filter. In “Faster Flow” mode, the water is directed straight to the glassfiber filter allowing filtration up to 2L/minute.
The Vario is compatible with most standard outdoor bottles and hydration bladders. The dual piston design ensures that water flows continously when raising and lowering the pump handle.
Another must have item is a pack of the Katadyn Micropur MP1 Water Purification Tablets. They can be had in packs of 20 or 30 and are the only EPA Registered Purification Tablets on the market. Use 1 tablet per quart (or liter) of water.¹Source: http://health.howstuffworks.com/diseases-conditions/death-dying/live-without-food-and-water2.htm