2015 ace 30.2 toilet issue

[J K]

Situation: fresh water tank full, black 3/4, gray empty. need to dump black, so dumping some fresh into the gray to get some water to flush through the system. fresh drops to 3/4, black increases to full, gray stays the same. soon the toilet starts bubbling up and sewage smell coming in from the toilet.

is there a link between the black and gray? some valve that I need to open? it seemed that the black was somehow filling up with waste water from the sink. is that possible?

[brad13]

My bathroom sink empties into the black tank.

[Larry]

My bathroom sink empties into the black tank also. Only the shower and kitchen sink empty into the grey tank.

[J K]

ah, well, that would explain it then. I thought only the toilet emptied into the black.

thanks for the responses