If you have documentation from Keystone that your units shower is supposed to drain to the gray and itís plumbed you the black, I would be sending copies back to keystone via registered/certified mail asking for repair if itís still under warranty.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.