I have a Thor Chateau 24F, and the 40 gallon fresh water tank is just left of the entrance door, under the kitchen sink area. By removing various kitchen drawers, I can access the drain handle... a vertical rod with a "T" handle similar to a dump valve handle.
Directly under the rig in that area is a short white PVC pipe sticking down from the tank. If I pull up that drain handle, the water blasts out of that PVC drain. Pushing the handle down closes the valve.
Are you SURE that's not the low point drains you're trying to turn? Then again, my low point drain valves are cheap little plastic buggers near the water pump.
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