Cheap and Simple DIY Dry Composting Toilet for a Van Build
Materials needed for this project →
- The box is made out of 3/4" plywood
- Wood glue
- Two 12" piano hinges
- Clear-coat to coat the inside of the box
- I got a regular all-stain brush from a local hardware store
- A sweet toilet seat
- Solids bucket
- Liquids container
- The white funnel-like PVC pieces are just from a local hardware store
- PVC cement
- Butyl tape
- Urine diverter
I’m here for ya.
Seriously! Reach out on Instagram or YouTube with questions.
The videos are good…this one shares TMI though.
Decide where you want your toilet.
Where to put a toilet…a big question for such a small van. I went back and forth on all sorts of ideas for where to put a place to poop. I settled on building it into my bed / couch.
This dictated the dimensions of the toilet. If you decide to put your holy seat in a bed / couch like mine, this will be perfect for you. If not, the parts I used will most likely translate to whatever you want to build.
Build your box within a box.
There are two boxes here, the box that is the toilet, and the box that contains the toilet. A box….within a box…whoa.
My main box is 16” wide, 16 3/4” tall, and 25” deep (to match the size of my couch which needs to be average height and depth for a sitting position.
The secondary box, the box within a box, is about 20” deep, 15” wide, and 13” tall which just barely fits the elongated seat, the solids bucket, and the shape of the urine diverter.
The small box is mostly made up of supports glued and nailed to the sides rather than wasting space running plywood all the way down the sides of the internal box.
The lids use 12” piano hinges mounted to pieces of plywood set flat on top of each box top as you can see on the left. The lids then extend beyond each of those mounting pieces to sit flush with the edge of the box(es).
Coat the inside of your box.
Let’s be honest, this is going to be a prime location for messes down the road. You want the wood to be as resistant to moisture and splash damage as possible while also being wipeable.
I used this polyurethane clear coat to coat all of the surfaces inside the box, the lid, as well as the inside of the lid that you’re about to cut the shape of the toilet seat out of (next step). I put on 4 coats in total.
Attach your toilet seat.
I used this elongated toilet seat since I am not a fan of tucking. Moving on.
I held the toilet seat on top of the inner lid, traced the inside, jigsawed out that shape, screwed the toilet seat to the lid through the underside of the lid (3/4” plywood and 1/2” seat = a 1” screw so as not to break through the seat).
NOTE: I took off the top of the toilet seat as well as the rear hinge to be able to fit the seat inside my box within a box. I also took off the little nubs on the bottom of the seat. I also shaved off the back of the toilet seat in order to make it fit on top of my lid without interfering with the piano hinge.
Attach the urine diverter.
I recommend fitting your lid with the seat attached and the hole cut out of it into the toilet box and lifting it up and down to make sure you can find the most forward-sitting position for the urine diverter while also still having the funnel of the diverter land where it can intercept the liquids jug.
Once you’ve found the optimal place for your diverter, simply screw it into the bottom of the lid (3/4” plywood + 1/8” thickness of the diverter = 1/2” screw so as not to break through the lid).
Make sure you clear coat the inside of that newly cut rim inside the outline of your toilet seat.
Jerry-rig your urine container! Yay.
I wanted to make sure I had a large reservoir for urine (so that it would not spill/splash when driving if I had one or two uses in it), while also making sure that the transfer from the diverter to the container was as contained as possible while still remaining easy to open (lifting of the lid and attached diverter) to access the liquids and solids containers.
This led me to drilling a hole in the jug, inserting two PVC pieces, one to act as a catch for the urine diverter funnel and one inside that catch to act as a reducer in order to reduce the likelihood of splashes making it out of the hole.
I also ran some left over butyl tape around the cut edge in the jug before inserting the PVC pieces in order to add a layer of liquid-proofness.
Secure your liquids and solids containers.
Once everything is in place and you have your lid re-attached to the box with the toilet seat in place as well as the urine diverter, identify where each container needs to sit (the bucket is easy, the liquids container has to be a bit more exact due to to the small size of the funnel on the diverter), and secure them using plywood slats. I made mine the same width as the box and bout 3 or so inches tall. When I screwed them into place, I made sure they were slightly smaller than each container to make sure the container was “squeezed” when in place to keep it in place.
I am super satisfied with how this turned out! I am anxious to see how odor control will go…I will try saw dust, peat moss, and (surprisingly) coffee grounds (the leftover stuff from when they make espresso) between each use of the toilet.
I don’t intend on using the toilet much at all…It is 100% for emergencies and peace of mind. So, my main odor control strategy will be to…not use it haha. I did not install a vent in the side of the van as some people do because I did not want to drill a hole in the van. If I change my mind, I can always go back and drill a hole if the smell is too bad.