I live in a 1 1/2 story Cape Cod with the hot water tank in the basement. It has a cold water inlet and a hot water outlet from the top of the tank which theoretically circulates the hot water and returns it to the bottom of the tank to be reheated and circulated again. It worked just fine until I had to replace the tank. Since then I run gallons of water at my second floor sink or shower before I have hot water. Theoretically, since hot water rises and cold water drops, I should immediately have hot water when I first open the faucet. I suspect it's an air block, but I don't know how to resolve it. Any suggestions?