Originally Posted by stjoenurse
We bought this unit brand new, I think it has always been an issue but we thought it was draining so we didn't realize at first it was actually leaving water in the tank until we figured out why it kept registering 2/3 full, so my husband opened it while we were parking it and found by stopping quick numerous times the tank finally completely drained. We just aren't really sure how to get into the tank without ordering a scope. He did try snaking it but nothing came out. He hasn't tried opening up the bottom of the RV to find the tank yet however that will be our next step after our camping season is over. I hate taking it into the shop for this but just might have to do it. I will keep everyone posted once we solve the issue! Thanks to everyone who offered advice.
Contact Jayco for the plumbing schematics! I had a problem with my black tank that sounds just like your issue. I found after putting a camera down there the valve was only partially open. With the schematics I knew right where to cut open the bottom and get to it. I ended up relocating the handle right by the drain pipe so now the cable is straight. Works great!
Are your valves on cables?? Hope this helps!