I finally completed the upgrades on the water tank in the car.  I installed a heat sensor and gauge and also a tank water level sensor and a gauge in the back to help us with filling.  In the initial design of the water tank we planned to have a separate filling whose in addition to the out pipe.  This wasn’t very practical however.  At some point I realized that we can fill the water tank from the out pipe.  The water pump has a 3000 psi reverse flow shutoff valve, so when you put water in reverse it actually flows in the tank.  This was super convenient for us since I did not have to remove all the junk from the trunk to get to the back to fill the tank.  The problem however was that we had no way to know when the tank gets full so to be conservative we would usually fill it half way up.  Well, not anymore :).  Now we have an awesome water level gauge so we know when we are out of water and when we are full … We have been taking awesome hot showers on the beach!  Yeah!