It’s Thermodynamic Thought; So we went on vacation for 3 weeks, and no sense of heating hot water so we took our morning showers, then water heater thermostat turned “down” to its coldest setting. The pilot light was still on but the water heater temperature setting was turned way down to where it will not come while we were gone. Then we washed dishes started dish washer, washed laundry in hot setting and did other cleaning using hot water faucets. Mid day, car loaded I checked the hot water temperature, it was barely Luke warm. Then to the car drove off. Fast forward return to the house 3 weeks later, the water was hot, scalding hot. How come Dad the water heater is off. Well did you ever heat water with a candle, I have only takes about 8 to 10 minutes for boiling hot water, right. A water heater pilot light is just like that candle and in three weeks you have a full tank of hot scalding hot water. Your paying the gas company for that pilot light so my point is if you go away for a length of time turn down the hot water thermostat and just let the pilot light slowly heat the water tank. Your welcome.