For years and years it has taken me nearly 10 gallons of antifreeze to winterize the 'Roo. I always thought "it's the bypass valve leaking into the water heater." Several years ago I took the valve out and tried to match it. No luck. Today I took it it out again and tried a more scientific approach - pour water through the inlet port with a funnel and see if it leaks out the port to the water heater when it's set on bypass. No leak - so does that mean the valve is OK, or just that it didn't have any real presssure to find a leak? So now, I wonder why does the water heater always flow anti-freeze when I'm putting it into system with the valve set to "Bypass"? I know that it's flowing because I have had the drain plug open to verify that. So, is there another valve somewhere I don't know about? I have heard there is a check valve on the water heater but do not know its purpose. And, it's virtually impossible to get at the back of my water heater to look for anything like that. I once had to get in there to fix a busted plastic line and had to remove the furnace above it to get anywhere near the water heater. I'll sure appreciate any advice. It's not that the antifreeze costs that much, it's just the nuisance of having to run so many gallons through. I searched but did not find bypass valve nor winterizing posts. Probably I just don't remember how to use Search, it's been so long since I've been active on the forum.