Originally written May 21, 2020
We decided to try to fit in a C402C Model. Rather than either a smaller portable cassette (self contained), or some type of flush RV toilet requiring a secondary holding tank that would need mounted inside, or hung beneath the van floor.
Being this build is in a 144 length Sprinter Van. Usable real estate underneath the van for tanks is very limited. Even if you can find, or have custom holding tanks and hanging brackets made. Mounting tanks underneath would also need to be planned in advance too.
We want that space for a Gray tank to capture sink and shower water. Also space for an external mounted LP Furnace, and LP tank.
One of my biggest concerns with a cassette type is. The possibility of gas/stink smells. (Read on, for a follow-up on this subject, 14 months later). My fears never came to fruition.
UPDATE 7/11/2021 After using this toilet while traveling, and actually camping at times during the “build” process. Also purposely leaving waste (#1 and #2) in its holding tank. While the van sat in the summer sun of Las Vegas heat.
The latest test was for 2 weeks, with outside air temperatures hitting 117°F. Hard to imaging the interior temperatures with the van closed up. I can vouch for the fact there is no apparent gas/smell release into the van. I am real picky about smells. So is my wife.
When I pulled the cassette to dump and dispose of the two week old contents. I can tell you the content was “ripe” while dumping. If there had been any gas/smell escape into the van it would have been really offensive.
So if you have the same fears I had. Not knowing the actual working performance of this unit. I feel confident this will not be a problem as long as you keep the seals in proper working order.
UPDATE 10/22/2021 After returning home from a 3 week, approximately 5000 mile trip. I though this update would be a welcomed evaluation.
It has been over a year since this unit was selected for our build.
I can attest to the fact smells escaping from the unit is not an issue. No more than any standard drained and vented RV type commode.
Of all things considered. Smell was my biggest concern doing the build out with this type of set-up. That has been put to rest for me.
The 5 gallon removable holding tank in our case, was mounted up high enough (when standing on the outside ground) it isn’t an issue concerning weight when full. (I am 69 at the time of writing this).
This portable holding tank is fairly easy to dump. It has a screw on capped, rigid swivel discharge pipe, that is about 12 inches long. I even stopped at a paid dump site at a truck stop, to empty once. No issues. Actually less fuss than dealing with a slinky hose.
The portable tank even has wheels and an extendable handle, so you could wheel it to a campsite dump drain if that was convenient when set up on a campsite.
We found there to be a bit of confusion on this model concerning which end the self contained holding tank is accessed from. Though some people indicate the 2 models found listed, are inter-changeable. By swapping their parts on the same unit? We didn’t want to have to mess around if you can order it as needed.
There is a model 32811 and a model 32812. The 32812 seems to be readily available on-line. Often the designation is only C402C. From what we could find out the 32812 is set up for access on the “Left”. Access on your left, when you are sitting down, assuming the useful position . We assume the 32811 is on the “right”. We never did find any helpful photos on-line to confirm.
We ordered our 32812 from Amazon due to their ease of returns should we assume wrong. When it arrived it did indeed have the waste tank access on the “Left” when sitting down. Just the way we wanted it.
It does appear as others stated, you could swap some parts around to make it work from the opposite end. We can’t absolutely confirm that though.
There is no cover on either end. It appears there is a base plate for securing the waste tank, that could be flipped?
In general the Thetford C402C is a totally self contained unit, with it’s own waste storage tank. We wanted the extra storage capacity over some smaller cassettes.
It has it’s own built in fresh water storage tank too. So the need to connect it to an external plumbing, or fresh water source, is not required. That was also something we wanted.
It has its own 12VDC electric pump/flush.
The Specs are as follows on their website:
Removable Seat and Cover for Cleaning
Waste Tank Capacity 5.1 gal (19.3L)
Fresh Flush Water Capacity 4 gal (15L)
Dimensions 26 3/8 Wide x 15 3/4 Depth, housing height 18 inches.
After we received the unit and installation.
I did measure the base that actually contacts the floor. It is 26 3/8 x 10 13/16. This includes the snap on toe kick trim on the base front.
So if you are dealing with close tolerances. The actual very minimal measurements for finished interior wall contact is 26 3/8 inches across the opening. The very minimum floor space contact from a finished rear wall to the front base is exactly 10 13/16 inches.
That wasn’t clear to me until I had the unit to physically look at. I held off on ordering any type of shower pan until I knew that dimension for sure. So glad I did. This becomes critical if you are buying or attempting to fabricate some type of step up from your shower pan level. I intended to fabricate my own shower pan that also sealed off the toilet from the van. A one piece hand laid custom fiberglass unit that has 3 ft high walls. Stepping the toilet up higher to clear a wheel well and maximize space.
I gave up on trying to find a combo type shower pan/toilet pan I could use as a one piece waterproof base. I searched endlessly on the internet. Saw photos of some completed installations that looked like what I wanted. But a fiberglass or plastic base that I wanted, in dimensions to accommodate the Thetford C402C, using minimal space, seems to not exist? At least not pre-made. One issue is this unit had to accommodate the vans wheel well as I indicated above.
It is really too bad such a pan is not out there on the market. It would be perfect for putting together a totally waterproof shower/toilet combo.
We are going to hand lay fiber glass on our own platform, and walls about 3 ft up. To create our own waterproof enclosure and shower pan. A one piece unit. The shower pan, toilet platform, and the partial walls, all fiberglass. The fiberglass verticals will be overlaid with FRP panels to create the shower stall the total height of the van interior.
The idea is, even if any of the caulking ever leaks, no water will ever be able to migrate through the fiberglass and down into the van. Any tank leakage or shower over spray, or even caulk leakage, will all route water down the shower drain.
Do you need a exterior access door/cover?
If you require an access door for the cassette waste tank to pass through. You will have to order that separately for the price of around $62+tax. Again more confusion. It appears the Thetford part number is/was 32144. But we couldn’t find that. Amazon and buyers, indicate you need to purchase Thetford Door 3 Including Zadi Lock (One Size) (White). (This one worked for us). It is just a body frame, with a hinged lockable frame for the door panel. You have to supply your own door panel to finish things off. Be aware this access door/frame is all plastic.
Combo Toilet/Shower build in progress. The bottom section is all one piece fiberglass that extends up above the top of the toilet height. FRP is bonded over it. Then the upper sections where bumped out slightly and the FRP is “lapped” over the bottom FRP about 3 inches, The overlap creates a waterproof caulkless seam.