Average water use per shower?

Back when we owned our Santa Fe popup I installed my own shower but because the FW tank was just 20 gals we really had to minimize our water use and as I recall the four us managed to get through each shower using about 3 gals of water. That was then, this is now, and I don't care how much water we use for each shower as there's now only the two of us so our consumption is probably twice that now. Quite frankly, having a hot shower at the end of the day is one of the best things we enjoy about camping in our travel trailer so minimizing water use is the least of my concerns. ;)