Thanks for the info RJsfishin, Joe417 and anyone else with useful information.
My tank doesn't have a pile under the spout, I start out with a few gallons in the tank after I dump, theirs plenty of water in tank to slosh when traveling and tank is filled before I dump and I rinse it good. Problem is not dumping and cleaning the tank problem is stuff getting stuck at the end of the pipe between tank bottom and pipe end. Sure I could use a ton more water then I already do when flushing but 100 gallons of fresh and a 50 gallon black tank isn't a lot of water holding capacity when dry camping for 15 days.
I would rather chance getting a pile of stuff under the spout that I could push free easier then trying to move the stuff that gets stuck between the tank bottom and pipe now. My thinking is if I shortened the pipe and started to get a cone of stuff a couple bowel fulls of water landing on top of it would break it up, right now all a bowl full of water does is plug up the pipe.
Some of my issue this time might have been a dry tank since I completely drained my holding tanks and reworked the dump line. The old hook up was a good 3 feet under the trailer and I hated having to get on my knees in who knows what the last dumpers left on the ground to remove the cap and hook up the drain hose so I removed the old pluming and reworked it so my cap now sets at the edge of the trailer and I can reach it standing up. About half way through the first day camping I remembered that my tank was dry and added a few bowl fulls of water to the holding tank but I'm sure it wasn't as much as I usually run with. Although this isn't the first time this has happened.