Find/access the backside of water heater (inside RV...opposite of where the outside compartment is)
On water heater will be cold water inlet to bottom of tank, hot water outlet at top of tank and the 'bypass' connects the cold/hot lines.
Some have shutoff valve on each (Cold/hot/bypass----3 valves)
Some have shutoff valves on cold/bypass (2 valves) with a check valve in hot out
Some have shutoff valves on cold/hot (2 valves) that are 3-way valves
Some only have shutoff valve on cold which is a 3-way vlave and a check valve in hot out
You have to trace lines and see how valves are used.