We replaced a gas water heater in our 1940's home with cast iron pipes. We found that water was coming into the water heater through the hot water pipe leading out of the water heater. Is this normal? We have checked the pipes to make sure we have the right one going in and out. The hot(which is cold) going out has almost as much water pressure going into it, as the cold has going into it. Is it back flowing somewhere? How would we find out where, and since it worked before, do we leave it? Our last water heater lasted 25 years. I have the water heater turned up quite high, but the water coming out is barely warm enough to take a shower.

Check to top of your heater, the two threaded openings are marked H and C. Check to see if your pipes match the heater labeling