This is an easy fix. Inside the valve you will find a small plastic piece that looks like a golf tee. Around the 'head' is suppose to be an O-ring. It came off and is preventing the valve from closing.
You will have to pull the hose connector from the camper, removing three screws and breaking the putty seal. Then disconnect the hose clamp.
You can then push the valve stem thru (it just snaps in) from the outside.
There will be a small spring around the valve stem.
Put the O-ring back on and put it back together.
I've had to do this twice now (some people never learn from their mistakes).
Next time we winterize, we need to remember to release some of the pressure by opening a faucet before pushing the valve in.
I hope this helps.
Me, DW and 5 dogs
2004 F-150 Reg Cab,Long bed 4X4
2008 Flagstaff 625D Pup (keeping this one for now)
2010 Jayco EXP 21M Hybrid
ďThis isnít rocket science; itís more like quantum physics.Ē