How to Make a Composting Toilet for Vanlife

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Introduction: How to Make a Composting Toilet for Vanlife

About: We're Laura and Louis. Laura is an educator and Louis is an engineer. With our powers combined, we make things and try to show everyone how we tackle projects in hopes to inspire others to get up and create!

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 some pre-manufactured toilets, we quickly realized it was out of our budget, so we decided to DIY our own solution.

So for this project, we'll show you how we made our own Composting Toilet.

We won't go into detail regarding the dimensions because this will vary for each persons' build and size constraints, so we want this instructable to serve as a general guide on the overall approach to build your own.

We made a quick Youtube video that goes through all the steps, so please check that out as well! (We would also appreciate a like and sharing if you think it's worth it :))

Supplies

Here is the list of supplies we used: (These are affiliate links where we earn a small commission at no extra cost to you, Thank you!)

4ft x 8ft 3/4" pre-finished plywood

1.25" screws: https://amzn.to/3qwqvgO

Toilet Seat: https://amzn.to/3cpEzUv

Piano Hinge: https://amzn.to/3sZ6Ac4

Soffit Vent: https://amzn.to/38juA1B

Adhesive Sealant: https://amzn.to/38juA1B

Computer Fan: https://amzn.to/38juA1B

Starbond CA Glue: https://amzn.to/38juA1B

Starbond Accelerator: https://amzn.to/38juA1B

Cereal Container: https://amzn.to/38juA1B

Urine Diverter: https://amzn.to/38juA1B

12V ON/OFF Switch: https://amzn.to/38juA1B

PVC Adapter with Plug: https://amzn.to/38juA1B

5 min Epoxy: https://amzn.to/38juA1B

Compostable Trash Bag: https://amzn.to/38juA1B

Liquid Container: https://amzn.to/38juA1B

Leather Pull Strap: https://amzn.to/38juA1B

Step 1: Drill the Vent Hole and Attach a Vent

Before we began building the actual toilet, and even before we put up the walls, we knew we’d need a vent hole to keep our toilet box and van stink free, so we started by drilling into the side of the van.

At this point, we only vaguely knew that we wanted the compost toilet behind the drivers seat, so we picked a random spot and went for it.

We used a 2” metal hole saw and started to cut from the inside of the van. Then we finished cutting the hole from the outside of the van because we thought it might help with keeping the burrs from getting out of control.

Next we grabbed a 2” soffit vent with a pool drain hose to use as the venting channel. We applied an adhesive sealant on the soffit vent flange to adhere it onto the van and used duct tape to connect the hose to the vent. We left the length of the hose long so we can cut it to size once the walls were up and we put the toilet in place

Step 2: Making the Box

We used pre-finished ¾” plywood and started making a basic box by attaching three walls and the bottom floor with 1.25” screws using simple butt joints, making sure to predrill and use a square along the way. You’ll see that we cut a hole on the back panel in the area where we installed the soffit vent on the van.

Step 3: Adding a Divider Panel and the Front Wall

Next, we added a divider panel that will separate the business area and the storage, where we’ll keep the toilet paper and cleaner.

Then we drilled some pocket holes on the walls so we can attach the front panel.

Step 4: Adding a Fan

We had an old computer fan laying around so we mounted it on a piece of scrap ½” plywood with a hole cut out in the middle to act as a spacer to allow airflow. We attached it to the back panel over the hole we cut out for the vent.

Step 5: Prepping for the Toilet Seat Lid

We want the business area of the toilet to be sealed off from the rest of the structure, so we can contain the smell, so we’ll be creating a lid to box out the area. To start, we attached a 3” wide strip along the back that’ll be used to anchor the toilet seat lid.

After measuring the height of the lid in the closed position, we added a small piece onto the front panel to act as a positive stop. We used CA glue and activator to hold it up while we secured it with 1.25” screws

Step 6: Securing the Toilet Seat Lid

Then we added the toilet seat lid. We attached it with a couple piano hinges so it can lift up and we can access the area underneath.

We placed the toilet seat on top and traced the mounting point and the seat opening.

Step 7: Cutting Out the Toilet Seat Hole

We drilled out the mounting holes first. Then we used a jigsaw to cut out the opening. We had to trim a few times to get the size just right. You want the hole to be larger than the opening of the toilet seat. having about 1" around the outside perimeter of the seat seemed to be the best balance.

Step 8: Attaching the Seat and the Diverter

The toilet seat installs with the provided hardware and once that was on, we placed the urine diverter about half way in the opening, attaching it with screws.

The urine diverter is the key to having a virtually stink free composting toilet. The combination of the liquid and solid is what makes the prominent sewage smell.

Step 9: Cutting Opening for the Liquid Container

With the diverter in place, we can mark the position of the spout on the liquid container. Using a 2” hole saw we cut out the hole, and used this PVC drain pipe fitting and glued it in place with 5 min epoxy.

Step 10: Sealing the Box

While the epoxy dried, we sealed all the corners with silicone. This will help contain any odors and any leaks should there be any.

Then we secured some scrap pieces down with brad nails to help keep the urine container from sliding around when we drive.

Step 11: Wiring the Fan

Before putting on the top lid, we drilled a hole for the rocker switch that will turn the exhaust fan on and off. We plugged the connections in and fished the remaining wire through a hole going into the storage area.

Step 12: Secure the Bucket

With the wiring complete, we added a couple strips of wood to keep the #2 bucket from shifting around while driving

Step 13: Adding Lid Stoppers and Pull Handle

We drilled a ¾” hole with a forsner bit about half way through the wall, so we can use this ¾” dowel as a stopper to hold the toilet lid up when we need to access the area underneath. We also added a simple leather strap to help pull the lid up.

Step 14: Adding the Top Lid

We attached the 2” wide strip along the back portion of the box. Thenwe put on the top lid and secured it with piano hinges, adding a lip to the front edge using pocket holes.

Step 15: Installing Into the Van

We brought the toilet into the van and slid it into place making sure to line up the exhaust hose we attached earlier to the hole we drilled in the toilet box. Then we secured it with 2” screws along the back wall and the floor

Step 16: Stocking Supplies

With the toilet secured in the van, we used cereal containers to hold the peat moss for composting, and a bottle of vinegar and water solution to use as disinfectant. They fit neatly into the side compartment with some toilet paper.

We keep a roll of composting trash bags that fit the #2 bin, in the compartment underneath the toilet seat lid.

Step 17: Improvements

After a few weeks on the road, we love our composting toilet and the added comfort having it in the van. It saved us a handful of times when there were no public restrooms available. The computer fan came in clutch to reduce odors while we were using it and we found it’s Crucial to completely cover your #2s with peat moss to minimize odors. And with the box closed, the van was virtually stink free.

We found a few things that could be improved. We built the toilet to accommodate both of us (6ft and 5ft) which led to a shorter than average seating height. So the liquid container we chose was wide and short to fit the available space. We found that it’s not conducive to bumpy roads when it’s more than half full as it splashes around. We see why other builds used taller jugs to avoid this from happening. Also, in order to lift the liquid container out of it’s spot, we wrapped a strap around it to use as a handle, but it’s not the cleanest solution. We’re still brainstorming a better fix. Last but not least, we added a gas strut to keep the top lid open because it had a tendency to fall when the van was not level.

Step 18: Subscribe and Comment!

Thank you for reading our Instructable!

If you liked the project, don't forget to share it. Comments and feedback are always welcome. You can check out our other projects here on Instructables as well as our Youtube channel IMEE MADE.

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    9 Comments

    0
    acarol123
    acarol123

    Question 2 months ago on Step 12

    what did you connect the wires, for the fan, to. Is it a 12 volt fan or is it battery like 9v or c cell batteries.??

    0
    imee made
    imee made

    Answer 2 months ago

    It's a 12 volt fan. We are using a Jackery 1000 solar generator to power all of our electronics on the van, so we have a 12v distribution panel that the fan is wired into.

    0
    acarol123
    acarol123

    Reply 2 months ago

    So you know a little about solar. Cool, I just recently built a she shed for my wife, 8 x 17 ft, want to power it by solar, any information or suggestions would be most welcome.
    Thanks Alan

    0
    imee made
    imee made

    Reply 2 months ago

    That's great! For our camper van, we used a solar generator (Jackery 1000- https://amzn.to/3fVOCDW). It's a good value considering all the factors in our opinion. There are many brands and they all have pros/cons but rule of thumb is $1/W. We keep it charged with 2 - 100W panels (https://amzn.to/39XCvlW) and have the option to charge it through mains power if needed.

    0
    acarol123
    acarol123

    Reply 2 months ago

    Thanks for the help. Take care alan

    1
    tytower
    tytower

    3 months ago

    I imagine peat moss is expensive . I use sawdust and no smell. Like the urine diverter .Best way is do it outside first but then women ,you know.
    A tank with baffles would be better but best would be foam filled like they do with racing car petrol tanks.
    Thanks

    0
    imee made
    imee made

    Reply 3 months ago

    Peat moss isn't too expensive and a little goes a long way. However sawdust is definitely more economical.
    Thanks for suggesting a baffled or foam filled tank that seems like a great route!