Seems like once every other week or so we wake up with no hot water. I have found a weird fix. If I go down to our laundry room (where the water heater is located) we have a utility sink in the room right next to the water heater. I will turn on the hot water on the utility sink and let it run for 5 seconds. I will usually hear some kind of "cough" and bingo, we get hot water back upstairs. What is causing this?