Black Tank, Grey Tank, New Tank, Old Tank
I am refurbishing the bath and fixing floor in my '68 Overlander. While tearing things apart, I found the toilet sits on a "riser" (plastic block 6" tall), as does the tub (plywood base). My model only has a single tank (black tank) that is 17 gal. This is under the floor and everything over it except the last 10" of floor is in great shape. For now, I will be replacing only that portion of the floor and reinstalling the original bath.
My idea is to add a black tank that would sit on the floor and replace the toilet "riser", and part of the tub riser. All of this is wasted space as originally designed. It measures out to be about 30" long by 24" wide by 5" tall assuming a rectangular tank is used. This would yield just under 15 gallons which is plenty for me. The toilet would basically sit on a platform over the tank. Tank would be vented out the Starboard sewer stack, and the outlet would be in the "service center and tie into the outlet from the old black tank now grey tank for dumping purposes.
I have read a lot of posts about adding weight in the rear of the trailer, etc. For my purposes, this will be less of an issue as the tanks will rarely if ever need to be full during transport. I also believe these concerns to be somewhat overstated assuming the trailer is in otherwise good condition structurally.
Is a 5" tall tank going to work OK as a black tank? Is there risk of "pile up" below the toilet? I could go to 6" or 7" under the toilet and down to 5" under the tub if I go custom.
I have seen tanks that allow toilet install directly on the tank with a notation that the tank is strengthened for this purpose. Any experience with this? I think I can add extra structure to support the toilet and its occupant quite easily if needed.
Looking for general thoughts and opinions.