Hi Guys.. I have the 2019 Redwood MB3901 - this is the two bathroom model.
My question is which tanks are connected to what in the RV?
On the I-Command control panel the two black tanks are named 1 and 2 as well as the grey tanks but in the panel where we open/close the valves both are named just Black and Grey..
Does anyone know which ones are 1 and 2?.
Thx so much..

You may have to work to figure that out.. Fill ONLY 1 tank, mark down which tank that is, go outside and pull levers to see which one allows the water to run out.

Tha is very much Joe. That was my next step.
Was trying the lazy route first lol

Not sure about the newer years, but with the 12's to 16's you couldn't guarantee that 2 coaches were plumbed alike. All depended in the installer on the floor.

Joe's given the best advice.

Tha is very much Joe. That was my next step.
Was trying the lazy route first lol

Clean & flush both the black tanks thourghly & before using again dump a different color package, or 2, of Kool Aid into each tank, both black & grey, to color the discharge then dump 1 tank at a time checking the colors then mark the pulls.

Thanks very much.

We have a 2013 31RL and I had questions about our grey (only 1 black). I used food color and found that Grey 1 was the shower and kitchen sink. Grey 2 is the bathroom vanity only. Not the most efficient use of 2 tank. I could probably only drain the Grey 2 once every 2 years. What I use it for is a clean flush. I run the sink for 20 minutes and drain it last to clean out stinky slinky.

Others have added the twist on valve to the RV end of their sewer hose then with it closed open both grey valves, this equalizes both grey tanks making better use of the tanks. Be sure to close both grey valves before dumping the black.
The bath vanity tank most likely is where the wash machine drains if equipped.

Thanks very much Will.. that's a great idea.

Using the extra gate valve to equalize both grey tanks only works when both tanks are installed at the same level. Not all floor plans are plumbed that way.

Chris is correct, and while I can't say for sure on a '19 unit, on our '16 MB the Bathroom/Washer drain into the Gray tank located in the drop down section next to the main Black, while the Kitchen/Galley tank is up in the Belly just in front of the axles next to the 1/2 Bath Black tank, if so equipped.

Thanks Chris!