Insufficient draining of grey and black tanks

[bigdawg51]

Purchased a new Coleman Explorer CTU297RE 2 months ago at a Campers World dealer near me. After 2 weekend trips found several things that needed fixed, minor in nature that I could have done myself, but it was brand new, so took it to a Campers World dealer closer to home. The big issue was the grey and black tanks do not drain completely. I open the black water valve first and wait, and wait, and wait. After waiting 10 to 15 minutes, I shut this valva and open the grey water valve ( which drains out of the same sewer hose connection. You can hear wand see water trickling for well over 10 minutes after the valve is opened. Then I reopen the black water valve and more black water flows. Frustrated I switch to the other grey tank, and again the same issue, water trickles forever. I have actually taken the hose off with the valve open and can see a small stream of water about the size of a pencil running out of the pipe. Has anyone else had this problem? I was told by the dealer that all of the warranty items were fixed except for the couch. I think not.
I am inclined to believe, the factory left the piece of the tank that they drilled out for the pipe inside all three tanks.

[Tanman]

I dont know how far it is from the outside opening to the tanks but I would open the gray tank unless the black has not been used and try to snake a water hose up the pipe into the tank. see if you hit the valve door of if it goes into the tank. If there is a piece of plastic you suspect the hose will push it out of the way and water will flow. If not you may have faulty valves.