My home has a Bradford White, propane, 40gal, Hot water heater. Mdl # is MITW40L6CX12. We are leaving for an extended period of time and I want to shut the water heater off. Instructions on the heater indicate that by shutting the electricity off, turning the heat adjustment down, and turning the gas switch "off", that I should be good to go. My question is, "Should I also shut off the gas line valve to the heater" Thank You, Gary Briggs Hayward, WI.