Taking a 10 minutes shower uses the most amount of water in an average house. This is because according to the facts, the shower sprays away 30 to 50 gallons of water in 10 minutes. In comparison to the shower, the toilet when flushed, drains away about 2-7 gallons of water.
This is still quite less as compared to the water drained after spending 10 minutes in the shower. Moreover, a bathtub when filled, makes use of 25-30 gallons. This is yet again, an approximation of the actual value which may vary. In the end, washing a single load of clothes makes use of 25-40 gallons.