I spent yesterday working on the gray holding tanks and related plumbing. It was a good day because I was able to get the various pieces to fit pretty much as I wanted.
Installing the gray tanks
. First, I had to fit the gray tanks (purchased from Vintage Trailer Supply
with custom fittings to suit my plumbing plan - VTS-851) into their respective belly pan bays. Each tank had fittings on either or both the front and rear sidewalls of the tank (that had to be lined up with openings in the cross-members), and each tank had at least one fitting on the top of the tank that required a hole in the subfloor of the coach.
Cutting holes for the gray tank top fittings
. I took lots of measurements and checked everything at least twice before I cut the holes in the floor. Based on my calculations about location of the tank in the bay and the location of the top fitting, I drilled a pilot hole from underneath the trailer and then went inside to make sure that I was satisfied with the location of the pilot hole. I then used my hole saw adapter to my power drill and cut (from the inside of the cabin) the holes, using the pilot hole to guide the hole saw.
The front gray tank is in the bay over the axle, and I could not get my drill into position to drill the pilot hole from underneath. I made some more calculations and then drilled the pilot hole down from inside the cabin. I was a bit off on one of the two, but I drilled an accurate second pilot hole and used that second hole as the pilot hole for the hole saw.
I was very
relieved when all the tanks ended up fitting as required.
Connection of tanks to dump assembly
. Next, I worked on connecting up the holding tanks to the dump assembly. Here is the starting point, with a steel pipe welded through the frame rail. The PVC discharge pipe from the two gray tanks will pass through the steel pipe and then join the Valterra dump assembly.
The Valterra will sit directly underneath the black tank, which sits on the floor of the wet bath. I still have some fitment to do because the Valterra assembly needs to be up against the bottom of the subfloor, and it does not want to do that. I will either have to reconfigure (shorten) the fitting (which I am reluctant to do because it is threaded) or raise the black tank off the floor (which I do not want to do because it will raise the height of the already-high toilet).
Here is the whole dump assembly (dry fitted and not attached to the black tank):
Here is the rough layout of the gray tank plumbing (without the tanks in place). One gray tank will be over the axle (the bay to the far right in the photo) and the other gray tank is in a bay to the rear (the bay to the left in the photo), leaving one open bay (the bay in the middle of the photo with the T and the two flexible fittings) for the plumbing to join the two tanks and connect to the dump assembly:
I spent lots of time on my back under the trailer on a mechanic's creeper, and that it not my favorite activity, but at this point everything seems to fit, so I am happy.