The techs at the rally in Goshen checked and the rig is plumbed correctly and what was happening was the tank sensors were not correct and that I should keep an eye on the level of the galley tank. They also suggested that when possible, if we are hooked to sewer, to keep the grey and galley gates open, which we have not been doing. But DO NOT keep the black gate open under any circumstance except when you are dumping the black tank.
This probably does not give you an answer that you can take to the dealer but have them check the tanks and plumbing. I have used Gel food coloring to check for proper drainage with other tanks so this could maybe help you and/or the dealer. We had other problems with the tanks and gates not properly closing so there was grey/galley slop in sewer outlet pipe when I would open cap to attach sewer hose.
Plant manager of the Sierra/Sandpiper factory himself
, came and put a fix on that will take care of this until the rally next year when he said they will replace/repair all tanks and gates in our rig. Good luck and join the Forest River Owners Group (Free) and try to attend next years rally. PM me if you like and we can speak about the superior customer service they provide at the rally.
2014 Sandpiper 35ROK
2004 Volvo VNL64T 630 left tandem
D-12 435 HP 740 CU
Western Golf and Country Cart (custom body, EZ-GO frame)
Arguing with some people is like trying to smell the color 9