The next case is one is which you have a valve on the cold water line and a bypass valve in the middle but there is no valve on the hot water line.
Rv hot water heater bypass two valve diagram.
The by pass system can be used to drain the water heater and to winterize the rv water system.
This is called a back check valve.
You may need to remove a cover to access it.
If your rv has a bypass valve these two pipes will be connected directly to each other using a third pipe.
Now go into your rv and find the heater from the inside.
When the by pass system is used it takes the cold water going.
The water heater by pass system is used to separate the water heater from the rv s plumbing system.