If your rv has a bypass valve these two pipes will be connected directly to each other using a third pipe.
Rv hot water heater bypass two valve diagram.
This is called a back check valve.
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.
The water heater by pass system is used to separate the water heater from the rv s plumbing system.
Cold water comes in at the bottom and hot water comes out of the top of the heater.
Now go into your rv and find the heater from the inside.
The by pass system can be used to drain the water heater and to winterize the rv water system.
Most rv manufactures today install water heater by pass systems on the rvs they sell.