What type of shower system you have installed, and especially the showerhead, will help decide how much water will be used over the course of a 5-minute shower.
With a low-flow showerhead, you can expect to use about two gallons of water each minute, equating to 10 gallons over a 5-minute period.
If a standard showerhead is fit, the shower will likely emit around an extra half gallon of water per minute, so a 5-minute shower will use in the region of 12.5 gallons.
*1 gallon = 4.54 litres.
