Water valve

Sounds like RV MFG used 3-way valves
1/4 turn to open, close or direct flow

Very common type of valve used

Example: uses two 3-way valves
*in Bypass Mode (handle points in direction of flow)

Definitely weird and have to wonder what justifies a 3-way.

Every trailer we've owned (4) have had the simple open and close with a alternate bypass valve.

Note:
Make sure the bypass valve is in the closed position to avoid cold water invasion.

Are you guys thinking its the setup with only 1 valve and the water heater exit has the built in check valve?

If I'm seeing correctly, that pic shows it in the bypass position for both valves, if the long ends of the handle are parallel with the long tubes, then it's in summer use.

There are 1 valve, 2 valve, and 3 valve setups. How many valves are there in the water lines behind your water heater. Until we know that, we can't really answer your question.

When you say that when the valves are turned fully either way, you get no water, it sounds like you are opening one valve and closing the other at the same time. Both valves would need to be open to get water. I am going to make an assumption that you have a 2 valve system. You need to try 4 different valve settings:
1. top valve left, bottom valve left
2. top valve left, bottom valve right
3. top valve right, bottom valve left
4. top valve right, bottom valve right

One of those will have both valves closed and you get no water, the winterized setting. Two of those will have one valve open and one valve closed and you get no water, never used. The fourth will have both valves open and you will get water, the summer setting.

If you don't have a 2 valve system, this is not applicable.

Ok thanks to all .this explains a lot.

kellem wrote:
Definitely weird and have to wonder what justifies a 3-way.

Every trailer we've owned (4) have had the simple open and close with a alternate bypass valve.

Note:
Make sure the bypass valve is in the closed position to avoid cold water invasion.

Sounds to me like the valve handle(s) are not properly attached.

Why 3 way valves instead of one way? Only need two of them insead of 3. Depending on the supplier may be less expensive that way.

Mine is also 3-valve (all single action)