There is no liquid more vital to our survival than water, and the need for clean drinking water systems gets ever more vital as natural clean water supplies dwindle.

Thankfully, systems such as reverse osmosis allow for water sources to be more easily purified, with additional filtration such as carbon and ultraviolet light helping to prevent the types of deadly diseases that can sometimes flow through unclean water supplies.

However, given that the human body is made up of nearly two-thirds water with an average adult human averages between 50 per cent and 65 per cent and children having a much higher proportion of their weight being water, how long can you survive without water?

The answer varies considerably depending on your lifestyle, where you live, your age and other health markers, given that you lose water through sweat and even exhaling.

Most healthy active adults can survive less than a week before the life-threatening effects of severe dehydration, such as increased blood pressure, organ failure, an inability to regulate body temperature, brain swelling and hypovolemic shock can take effect.

The longest time any person has been recorded as surviving without water is Andreas Mihavecz, who due to the most wretched of circumstances survived on impossibly small amounts of water for 18 days.

On April Fool’s Day, 1979, Mr Mihavecz, then an 18-year-old apprentice bricklayer was put in a holding cell by mistake after being found in a crashed car but was forgotten by the three policemen meant to take care of him, each of whom believed the others has freed him.

He screamed for help, but given that his cell was in the basement of the Bregenz police station, they were not heard for 18 days, when he was found by chance by another officer.

He lost nearly four stone in weight and took several weeks to get back to health, highlighting the importance of keeping hydrated.