Kodiak Black Water Information
Looking online, the 2017 version of the Kodiak Ultimate has the bathroom on the rear. We have a 2021 Ultimate, model 2921FKDS with the bathroom in the center, separating the bedroom in the back and the living area in the front with pocket doors, so the actual routing of the plumbing is different.
The key information I can offer is the drain valve in our model is a slide valve built into the bottom of the tank, not a valve in the drain line itself. The valve is activated pull pulling a handle attached to a cable that in attached to the valve.
We had a problem with draining the tank. The cable felt loose so I thought the cable had detatched from the valve. We (traveling RV mechanic and me) cut open the pan to be able to see the valve action. It was working fine. The issue was it was the opening from the valve into the tank was blocked. We filled the tank all the way and the extra pressure pushed the blockage out.
If you have to find the valve, ours is a straight line from where the drain line goes into the pan under the camper. We were able to trace the path of the cable by listening to it scraping the bottom of the pan as we pulled and pushed the cable. It is a long round loop.
If you have to cut a hole in the bottom, make sure you leave one side connected. Tape it back up with Zip System Flashing Tape. You can get it at Lowes. It costs much less than the specialty tape the OEM recommends and is just as good.