black tank fill mystery
So I have a mystery. I recently purchased a 2022 Forest River Wildwood Heritage Glen 36FL Elite series 5th wheel. I took it on its first trip last week for 5 days, getting back last night. This morning, I went to the local camping world and flushed both of my 2 grey and 2 black tanks. (I have had a travel trailer previously, so I know the process). I then brought my camper back to my house and proceeded to sanitize the freshwater tank as I had to put well water in my fresh tank halfway through my trip. When I started, my black tanks were reading empty. During my second rinse cycle, I noticed my black tanks were at 2/3s full again. I hadn't used either toilet since I flushed them at Camping World. I had been running the water through my kitchen sink, both bathroom sinks and my shower to flush the bleach water. When I stopped using my bathroom sinks, the black tanks stopped filling. I took it back to camping world and sure enough, both my black tanks had quite a bit of fluid in them, so my sensors weren't wrong.
I thought all rv sinks drained into grey tanks. is it possible that my bathroom sinks drain into my black tanks? i can't think of any other reason that my black tanks would have filled back up as I didn't think there was any other connection between my grey and black tanks. Anyone else have any ideas?