This is the scoop, if you plan on taking showers every day in the trailer, you might have enough water for two days. If you use the campground facilities (showers and potty) as much as possible you can make it a week easily. We have similar size tanks, we use the campground facilities as much as possible, we regularly camp with electric only; we can go a week and use only half the water in the fresh water tank. Basically, the only water we use is for potty at night, washing dishes, and cooking/coffee.
It's up to you how long its going to last.
