Took our 2015 Bounder 35K on it's maiden voyage this weekend.  We found no major issues, until we returned home and attempted to dump the tanks.  On our previous two coaches, when we open the knife vales, there was a rush of effluent from the black tank. On this coach, with the vacuum flush system, it did not flow in a big rush. Maybe a couple quarts come down.  I watched it through the clear hose attachment, then a trickle.  If I pushed the knife valve in, waited a bit, and opened it, about another quart or so would fall. I had my wife start up the vacuum system, and then stand on the flush valve to let water flow back into the tank.  That did not appear to help at all.  What did happen, was I started to see a liquid flow around the fuel tank under the coach.  I crawled under the coach to see where the liquid was coming from, and started to smell urine, when I peered up over the fuel tank.  I was coming down between to objects above, that I could not identify.  At that point, I stopped the process.  Not ever having a vacuum flush system, I do not know anything about the process.  The owners manual does not really explain anything about the vacuum flush system.  It says,"Please refer to the toilet operating manual in your Owners Information Package."  Unfortunately, there was no such toilet operating manual in our Owners Information Package. 

The tank monitor is still showing at least 1/3rd full in the black tank.  Had no problems with the grey water.  This frightens me.