Leaking fresh water drain valve

[Jenp101]

We have a 1995 Jayco Eagle Series travel trailer. We noticed after we filled the fresh water tank that water was leaking out the drain valve underneath the camper in a nice steady stream. After 2 nights all the water was gone from the tank. The valve is in a semi-easy spot to get to. We tried tightening the valve and untightening the valve a little. Nothing worked. The valve looks great and nothing is leaking in or around the valve itself; which is why we don't really want to take the valve out. We have found that in older campers if it isn't actually "broke", don't take it apart as it can lead to even bigger problems. The parts and pieces are used to being in those spots after so many years! Any thoughts here? Could we maybe put something in the drain underneath the camper and clamp it off so it doesn't leak out?? Any suggestions would be greatly appreciated. Thanks.

[Nmgypsy]

Could it be coming from the fresh water overflow valves?
.just this AM, I noticed a drip underneath my 2011 Jayco Eagle Super Lite 5th wheel 31.5,

In checking the fresh water tank indicator it's still showing full even though the water was flowing out rapidly. I had the city water on, was not using the pump, was not filling the tank and the water continued to flow out of the Overflow. Some of the answers in Prior questions have sounded as if the fresh water overflow happens when the water sloshes around or the tank is overfilled but I have not moved my RV in several months, I am using the same connectors to the city water that I have used for several months, have not filled the tank for several months. I cannot understand why my overflow is suddenly overflowing?