Black tank shut off/leak?

kohai wrote:
I just finished a 12 day road trip with the RV -- about 1600 miles total. The very last day I drove 300 miles home and stopped to empty the black tank at the nearby RV park before putting it in storage. There was a couple thousand feet Elevation change in that 300 miles.

I was surprised when I took the cap off to hook up my hose that about 1 gallon of black tank came out. Luckily I had put a bucket under it so I caught it all. It stopped after about 1 gallon even though the tank was pretty full (handles pushed in/closed).

I then proceeded to empty the black tank with the hose hooked up and the black tank flush going (hose hooked to it adding water to the black tank). I then closed the black tank valve, filled the black tank, and emptied it. No sign of leaking. I did this twice and it worked as normal.

Any ideas why I would end up with 1 gallon coming out and only 1 gallon? I kind of expect all of it or none of it.

the gate valve may not have been closed all the way. that happened on our 2000 Suncruiser. until I could replace the valve I used a cut down bucket under the connection point. never got much more than a 1/2 cup, though.