We are planning to stay in MH this winter. Do I need to leave the water heater on all the time to keep water from freezin or can I just do like I do now and just turn it on when needed ?
Just turn it on when needed. Change of state from liquid to solid takes a huge amount of energy. Think about how long 1/2 cup of water takes to freeze in the freezer. Then think about how long it would take 6 gallons of water that is starting out at 140 F to freeze.