Not that I'm an expert... But if the pressure relief valve is popping off, you have another problem. These hot water tanks are as carefree as your hot water tank at home... Turn it on and forget about it till you leave.
I have often wondered about having both the gas and electric heating elements on simultaneously... I always assumed it had to be one or the other? So running both at the same time heats the water faster?
2015 Coachmen Apex 288BHS
2014 Toyota Tundra CrewMax 5.7L