Good idea
We went on a camping trip and used a bilge pump with a pressure switch and just connected to a shower head. The pump and switch were hard wired to a small battery. When you used water the pump would automatically turn on then off when you were done. We were also just dumping water into a 5 gallon bucket because we were camping in a livestock trailer, but it would work on the trailer if you put a water hose fitting instead of shower head. That way you wont even be using the RV tank and pump.