Recently we got a 140" wheel base Dodge Sprinter to convert to a camper for long road trips and camping adventures. One thing we absolutely had to have is a toilet inside the van. After researching pre-manufactured toilets, we quickly realized it was out of our budget, so we decided to DIY our own solution.
Materials needed
4ft x 8ft ¾" pre-finished plywood, 1.25" screws, toilet seat, piano hinge, soffit vent, adhesive sealant, computer fan, CA glue and accelerator, cereal container, urine diverter, 12V on/off switch, PVC adapter with plug, 5-minute epoxy, compostable trash bags, liquid container, leather pull strap.
Construction
Creating the vent
We drilled a 2" hole through the van wall with a metal hole saw. A 2" soffit vent with pool drain hose served as the venting channel: sealant on the flange, duct tape on the hose, left long to trim after wall installation.
Building the box
Using pre-finished ¾" plywood, we built a basic box with three walls and a floor using 1.25" screws and butt joints, with a hole cut in the back panel to align with the vent. A divider panel separated the business area from storage for toilet paper and cleaning supplies.
Installing the fan
An old computer fan mounted onto a ½" plywood scrap spacer with a center hole for airflow, attached to the back panel over the vent hole.
Sealing the business area
A 3" strip along the back anchored the toilet seat lid, with a small stop piece on the front panel and piano hinges for lift-up access underneath. We traced the seat's mounting points and cut the opening roughly 1" larger than the seat's outside perimeter.
Installing the urine diverter
The diverter sits halfway into the opening, secured with screws. Separating liquid from solid waste is what keeps the smell down. We marked the diverter spout position on a liquid container, cut a 2" hole, and glued in a PVC drain fitting with 5-minute epoxy, sealing every corner with silicone to contain odors and prevent leaks.
Electrical wiring
Before attaching the top lid, we drilled a hole for a rocker switch to control the exhaust fan and routed the wiring into the storage area.
Securing buckets
Wood strips kept the waste bucket from shifting while driving. A ¾" dowel, seated in a Forstner-bit hole, served as a prop stopper for the lid, pulled up with a leather strap.
Van installation
The finished toilet was positioned to align with the exhaust hose and secured with 2" screws into the wall batons installed during the van build.
Supplies and maintenance
Peat moss (stored in a cereal container) handled composting, with a vinegar-and-water solution as disinfectant. Compostable trash bags lined the waste bin. Fully covering solid waste with peat moss kept the van virtually odor-free.
Lessons learned
The seating height was shorter than average to fit the van, which meant a wide, short liquid container, a problem on bumpy roads once more than half full, since it would splash. A taller jug would have been better, and removing the container for emptying wasn't the cleanest process.
The top lid also tended to fall shut when the van wasn't level, so we added a gas strut to keep it propped open.
Update (January 2022)
After a full year of use, we made a significant change. The urine diverter, while functional, was clumsy in practice. Emptying was occasionally messy and bumpy roads caused splashing.
A YouTube viewer suggested pine pellets (commonly used for animal bedding) as an affordable alternative to peat moss or coco coir. They absorb liquid and odor effectively. We eliminated the urine diverter and separate container entirely: the waste bucket rotated 90 degrees, lined with a trash bag and pine pellets, letting all waste combine in one bucket. It gave up separate solid composting, but made the system far easier to use and maintain with virtually zero odor. This simplified design is what we're carrying into future builds.