The following photo is the valve bay with all the parts installed. You can see the clamp for the external drain fitting is already loose and slid back along the 3" drain line:
Note the big red arrow! You can see I cut the belly pan further inboard than necessary. I thought it was a cross member, but it turned out to be a galvanized enclosure for the black tank. The good side to this is that it protected the tank, but the bad side it that it's the full height of the space, so there is no space between the belly skin and the bottom of the enclosure, making it impossible to rivet the skin back together (no clearance on the inside for the rivet foot). Repairing, replacing, or attaching a cover in this area is not simple. Your best bet would be to leave at least 1" of belly skin outboard (to the street side) of the edge of the enclosure, so that you have an edge you can screw or rivet a cover plate to. The edge of the enclosure is not parallel to the frame (the frame is roughly parallel to the edge of the skin in the upper part of the photo).
A close look at the black valve reveals it can be removed by simply removing four large screws. The gray valve is not so simple. You have to disassemble the valve body by removing 9 screws into a space the is too narrow to accept even a Craftsman shortie screwdriver. You need one of those little "T-shaped" scredriver devices which include a ratchet (photo on request--I bought mine from Sears about 35 years ago and have only used it twice, but it's worth it's weight in gold when you need it).
So, four steps and the assembly can be removed:
1. disconnect the black valve
2. disassemble the gray valve
3. undo the shafts to the handles
4. undo the clamp on the drain line
When you pull out the gray valve you destroy the gasket. Can't be helped, it's such a tight fit. A new gasket comes in the repair kit (my valves were the all-pastic type, repair kt number is Thetford 09872, about $19 each).
Note: all connections eventually lead to a clamp, so everything can be removed and repaired/replaced. The plastic body that the black valve screws into is clamped to the black tank. The main drain has a clamp where the pipe goes through the frame, and the gray tank is clamped about 4" forward of the valve on the other side of a reducing fitting. The actual gray drain is about 1-1/2" diameter, but I didn't measure it. One other thing to note. After I took the valve assemble out, I finally saw the gray clamp and decided I'd need that to be loosed to get the valve back in. That fitting is so tight, that even after loosening the clamp, I could barely move the half of the valve body still attached. This is one mother of a tight fit.
Next: PUTTING IT ALL BACK
thanks for the notice TOM W! The top post in this thread was #1000 for me. Nice to be able to add something productive at such an auspicious time.
Zep