Found water in compartment......Water scalding hot after traveling full day.......(You must be working engine pretty hard.....engine aid should only get water to 130*F after 2-3 hrs. of driving)
If that water is in the outside compartment then:
Water is probably leaking from the PRV.
Water system on rv's is a closed system so as the water heats it swells and pressure builds....PRV drips
If that water is inside the rig around water heater than suspect leak in engine heater exchange.....either leaking at hose fittings or possibly from 'heater tube' on backside of tank