Originally Posted by henkelm
Can anyone post a picture of the hot water heater bypass so I no which one to close before winterizing.
If you have the three-valve system, then there are actually three valves that must be turned, like below. The valves are open when the handle is parallel with the line it's on, and closed when the handle intersects the line it is on.
It's also possible you have only two valves or even one. However the 3-valve system seems to be the most common.
In the 3 valve system, for winterization purposes, you want to close both the cold water inlet line and the hot water outlet line that feed directly in/out of the water heater itself. Now this shuts off the possibility of antifreeze getting into the water heater tank.
You now want to OPEN the bypass valve that ties the cold water line into the hot water line. This way you can pump antifreeze into the cold water line, and now since you opened the bypass valve, this antifreeze can also go into the hot water line in order to protect the hot water line from freezing too. It's called a bypass valve cause you are actually bypassing the water heater.
So for winterization: Cold in valve closed, hot out valve closed, bypass valve open
If you didn't have the bypass valve that connects the cold water line to the hot water line, then you wouldn't have a way to easily pump antifreeze into the hot water line from the cold water side (since you have blocked off your water heater with it's two valves, and it would have to be done a different way. Also by shutting off the water heater tank, that is 6-10 gallons of antifreeze that doesn't have to be used. You just drain the tank itself for winter, and it's good to go and won't freeze up since there is no water in it.
Here is a diagram of the typical RV water system: