hot water

So I bought a van that devoted significant real estate to a separate shower only to find that firstly you had to wait 15 minutes from the previous persons shower before you could be guaranteed some sort of hot water experience. Even then - unless you ran the shower at dribble speed, you never...

I have a suburban hot water system inside the van and our last trip the unit is working fine but if i leave the pump on for water when running 12v the over flow of the hot water just keeps pumping out water. I have checked the relief valve released pressure and turned back on but same result...