Update:
I finally got around to attacking this problem. So far, it is proving to be one of my most challenging RV DIY projects... (removing the black waste tank). This is on a 2015 Thor Majestic 28a.
When I removed the toilet, the black waste tank isn't immediately below (which would have been nice I think). Instead, there is a black waste line at about a 45 degree angle for about 2 feet (towards the front of the RV) and then goes into the black tank. This has made it VERY difficult to see anything. I tried rotating and wiggling the waste line (after unscrewing the flange from the floor) to see if I could slide it out of the black waste tank (assuming there is a rubber connector/grommet) but it wouldn't budge.
I tried attacking this problem from any possible access point (things are REALLY tight and not accessible). I tried removing drawers and items from underneath the kitchen sink, no luck. I tried from underneath, no luck. It even looked like if I removed one of my exterior compartments (trim + compartment) I might be able to get access...no luck. I was finally able to get a little break when I removed the heating vent cover in the bathroom and removed the flex tubing. Then, I could finally see/feel that black waste line. I could see that there was a straight piece of ABS going from the flange to the black waste tank that was at least 1 foot long. So I figured I could cut it in the middle as I could always re-assemble that part with a coupling later. So that's what I did. Then I was able to remove the flange with ~10 inches of the waste line from where the toilet was mounted. Wow...this hasn't been much fun yet. lol. I'll include some photos in a final write-up once I make more progress.
Now that the toilet flange and part of that waste line is removed, I can see even deeper underneath towards the waste tank and I can finally see where the vent pipe is shooting down into the waste tank. It is VERY tough to reach.
I thought (hoped really) that at this point I would be able to remove all the brackets holding up the black waste tank along with the exit pipe to the blade valve/dumping pipes and that the entire black waste tank could be dropped down. The only thing holding it at this point is the vent pipe. The problem is...I don't know if the vent pipe is simply slipped into a rubber grommet and therefore the tank will drop easy, or if the vent pipe is glued into the black tank and need to be cut. So I removed all the brackets, supported the front of the tank with something so it could only drop ~1" (the vent pipe and waste line to the toilet are at the rear of the tank) and attempted to wiggle/shake/pull/coerce the black waste tank to drop completely. Sadly, it did not. Ugh! I can get a finger up onto the topside of the tank where the vent connection is and I can feel what seems to be silicon of some sort (it feels flexible), but the pipe doesn't want to slide out. I think I am going to have to cut it from the top (through the toilet flange hole in the bathroom floor and the ~5" heater vent opening (....it is very tight).
The only other way I can see gaining a little better access is to put my RV on jack stands (just the rear driver side) and remove both wheels on the driver rear and then cut away the hard plastic wheel well (or part of it). Opening that up would give me almost ideal access. It *almost* looks like the entire wheel well cover is removable (....does anyone know???), but part of it looks like it was installed under some of the metal framing and doesn't look like it will come out if I remove the screws holding it in.
I haven't thrown in the towel yet! I'll keep you posted.
-Chris
