It was all in the way Lez pushed on the 2 x 6.
The day started sunny and warm as predicted, so Lee jumped in (more like, laid down in) and took apart the black tank valve in order to re-seat the seals. Using the car jack to raise the pipes slightly and having Lez strong-arm a 2x6 to pry the two open, out came the valve assembly, which we then cleaned up and reset the seals. Then back in with the same strong-arming and it was in correctly. Not the easiest for Lee's seventy year old body to wriggle in and out from under the Schooner, but the bolts went in and were tightened. No leaks, we were done. Time to rest the bones.
Lez takes in the rays: Although I wasn't outside much, the last evening's low of 5, morning 7 and rays of sunshine felt great as I offered my superior strength to make it possible for Lee to complete a shitty job. BIG grin - black tank on an RV is the holder of our "human waste" - which gave Lee the wonderful opportunity today to take his own stinky duds to that very same laundry facility after successfully replacing the valve. Now, only two more tanks to go - filled with "grey" matter. I think I hear a hair dresser calling!