How to drain a RW 4001LK

[Mike & Karen]

We just got our 3rd Redwood RV! It’s beautiful! But we tried to drain it for the first time, and noticed there are only 3 levers, and 4 tanks. Are we missing something? Does anyone out there have a 4001LK?
Please, if you can help, we would really appreciate it! Thank you KRen

 

[Travelin' Texans]

Don't know about the 4th valve, but am wondering what the 4th tank is for.

 

[R time soon]

Looked at the floor plan and it appears there is a rear kitchen. So my guess would be there is a separate gray tank at the rear of the coach for the kitchen. Since it is so far towards the rear, it is impossible to plumb the drain to have continuous 1/8" per foot of slope and not interfere with the axles to tie in with the other drains, I would assume there is a separate pull handle for that rear tank under the skirt metal in the back. Look for the separate termination too.