Water: the gold of the future | Photo: Tim Geers

Americans use twice the amount of water they think they do, according to a study by Indiana University.

Results show that participants underestimated water use by a factor of two on average, with large underestimates for high water-use activities.

High numeracy scores, older age, and male sex were associated with more accurate perceptions of water use.

Overall, perception of water use is more accurate than the perception of energy consumption and savings previously reported, however perceptions of both resources show significant underestimation.

When asked for the most effective strategy they could implement to conserve water in their lives, or what other Americans could do, most participants mentioned curtailment (taking shorter showers, turning off the water while brushing teeth) rather than efficiency improvements (replacing toilets, retrofitting washers). This contrasts with expert recommendations.

Shahzeen Attari, assistant professor in the Department of Public and Environmental Affairs at Indiana University, concluded "we may be underestimating how much water toilets use, because we use them frequently throughout the day."

A standard toilet uses about 3.5 gallons of water per flush, while a low-flow toilet uses 1.6 gallons or less. The average length of a shower is 8.2 to 8 minutes.

According to experts, humans require 13.2 gallons of clean water each day to meet basic needs. In 2005, the average American was estimated to use about 98 gallons per day.