Sewer question

[jburgessx2]

As a full timer, I usually leave my gray water open except when I want to drain
the black water. So, I close the gray water to let it build up so I can use it
to clean the hose after I dump the black water. And, I have done this for years
and years and years with my Beaver. Well, I forgot to close my gray water off
to let it build up and I knew the black water was getting close to full. So, I
close the gray water gate and turn on the bathroom faucet to let the gray water
tank fill a little so I have some hose wash down water.

After about 5 minutes of running, I smell black water and head to the bathroom
only to find the toilet overflowing on the floor.

Since when does the gray water (bathroom sink) go into a black water tank?????
To my understanding, the black and gray water are never to meet or they can
contaminate the gray water tank or contaminate the gray water pipes (i.e.
sinks).

Luckily, not much water escaped to the floor and I removed the carpet to wash it
outside. Of course, some seeped into the floor area (as any liquid will do).
So, I have a little more cleaning/drying, as well as some serious disinfecting,
to do.

Are Wanderlodge pipes plumbed different?

Jerry
85 PT40