Black tank doesn't empty always

[Rich205]

I purchase a Solitude 3 months ago and gone camping with it 4 times so far three times when I have tried to dump the black tank when it has been 3/4 full I get little to no water coming out even when putting a clean out wand in the toilet but after taking for a ride and pulling the dump valve it comes rushing out. Now on one of my old campers I had a piece of plastic blocking the gray water dump that when it was built they cut the hole in the tank for a connection and left the cut out in the tank so with that said does anyone have and solutions for me. we do use lots of water when flushing

[Country Campers]

It is possible that the cut out , or both one for the toilet inlet and one for the roof vent , could have been left in the tank. I is interesting that after travel it rushes out. The only thing I can think of from that is you are getting a clog right at the tank exit. GD seems to drop the toilet drain right at the tank exit and if there is a lot of paper or waste that accumulates there is would hold back the water.

Brian