The heat exchanger was fixed by a radiator shop. It was a small leak in an area that was accessible. If I get another 5 years out of it I will be happy. I am thinking about putting a bypass valve in front of the heater. Only run the water through when I am heating. When its not heating bypass the heater and open the drain valve on the manifold to avoid any corrosion or wear. Anybody have any thoughts on this idea and or suggestions on how to do this.