Two years ago we filled our 50 gallon propane tank with the max 42 gallons of propane
Last year we got an idea from a friend while camping and I immediately implemented the idea.
His idea works great for our little, old, non computerized 1989 coach.
I purchased a hot tub timer at our local big box lumber supply store for about $15.
I cut a hole for the switch backings on the cupboard wall on about where your right hip would touch the cabinet when washing dishes.
I then tapped each wire onto the existing water heater switch wires on the back of that switch. Now, when we want water for dishes or something we set the hot tub timer ahead of time (about 1/2 hour) and we have hot water for dishes, etc. No forgetting to shut the water heater off for almost a day and find out that the water heater was calling for propane whenever the water temp dropped.
Works great. Doesn't take long to heat up six gallons of water. The savings on propane at current prices more than justifies the price of the hot tub timer switch---and NO batteries in the switch!!!!