If you're living off-grid or just looking to save a massive amount of water, building a diy composting toilet with urine diverter is probably the smartest project you can tackle this weekend. I know, talking about toilets isn't exactly high-class dinner conversation, but once you realize how much sense it makes to stop flushing five gallons of clean water down the drain every time you pee, you'll never look at a standard toilet the same way again.
The reality is that conventional plumbing is a bit of a weird luxury that most of us take for granted. But for tiny house enthusiasts, van lifers, or anyone with a remote cabin, it's just not practical. This is where the magic of a composting setup comes in. It's simple, it's effective, and if you do it right, it actually doesn't smell at all.
Why You Need a Urine Diverter
The biggest mistake people make when they try to go the DIY route is just using a single bucket for everything. Let me tell you right now: don't do that. When you mix urine and solids, you get a chemical reaction that creates that classic "sewage" smell we all hate. By keeping the two separate, you're basically preventing the stink before it even starts.
A diy composting toilet with urine diverter works by catching the liquid in the front and sending it through a hose into a jug or a greywater system, while the solids drop into a bucket in the back. This keeps the solids dry. Dry waste equals no smell. It sounds too simple to be true, but that's the science of it.
Gathering Your Materials
You don't need a degree in engineering to pull this off. Most of the stuff you need can be found at a local hardware store, or even in your scrap wood pile. Here's a basic rundown of what you'll want to have on hand:
- A sturdy plywood box: This is the "throne." You can build it to whatever height feels comfortable.
- The urine diverter (separator): You can buy these online—they're usually plastic or fiberglass inserts that sit right under the seat.
- A 5-gallon bucket: This is for the "solids."
- A liquid container: A 1-gallon or 2-gallon jug usually works well.
- A standard toilet seat: To make it feel like home.
- Venting materials: A small computer fan and some PVC pipe or flexible hose.
- Hardware: Screws, hinges (so you can lift the lid to empty it), and some silicone caulk.
Building the Box
First things first, you need to build the housing. I usually suggest using 3/4-inch plywood because it's sturdy and won't flex when you sit on it. You'll want to build a box that's roughly 16 to 18 inches high—basically the height of a chair.
Make sure the interior is spacious enough to hold your 5-gallon bucket and your liquid jug side-by-side. I like to put the lid on a hinge so the whole top of the box flips up. It makes it way easier to pull the buckets out when it's time to empty them. Nobody wants to be fumbling around with a full bucket in a cramped space.
Installing the Urine Diverter
This is the most critical part of your diy composting toilet with urine diverter. When you cut the hole in the top of your plywood box, you'll need to mount the diverter so it sits flush under the toilet seat.
The diverter is essentially a funnel. The front part catches the liquid and directs it into a tube. You'll want to run that tube directly into your liquid jug. To keep things clean, make sure the tube goes a few inches into the jug so there's no splashing. A little bit of silicone caulk around the edges of the diverter where it meets the wood is a good idea to prevent any "misses" from soaking into your plywood.
The Importance of Venting
If you want your bathroom to smell like absolutely nothing—or maybe just a hint of wood chips—you have to install a vent. Even with a diverter, the solid waste needs some airflow to dry out.
I've found that a simple 12V computer fan works wonders. You cut a small hole in the side of the box, mount the fan so it's blowing air out, and connect it to a PVC pipe that leads outside your structure. This creates a constant "negative pressure" inside the box. Any odors are sucked out and pushed outside before they ever have a chance to drift into your living space. It's a game-changer.
Choosing the Right Cover Material
Once you've got the hardware set up, you need to think about what you're putting in the bucket. Every time you use the toilet, you'll want to toss in a handful of "cover material." This helps the composting process and keeps things looking (and smelling) clean.
Most people use pine sawdust, but coco coir is another fantastic option. It's highly absorbent and comes in compact bricks that are easy to store. Some people even use peat moss, though that's a bit less environmentally friendly. The key is to make sure the material is dry. You want it to soak up any residual moisture in the solids bucket.
Managing the Waste
Let's get into the nitty-gritty: emptying the thing. This is the part that scares people off, but it's really not that bad.
The urine jug will fill up much faster than the solids bucket. Depending on how many people are using it, you might be emptying the liquid every day or two. You can pour it out in a designated spot, or if you're in a more rural area, some people dilute it with water and use it as a nitrogen-rich fertilizer for non-edible plants.
The solids bucket, on the other hand, can usually go for a couple of weeks if it's just one or two people. When it's full, you can dump it into a larger outdoor composting bin where it will break down over the course of a year or so. By the time it's finished, it just looks and smells like rich garden soil. Just don't use it on your vegetable patch unless you've done a lot of research on hot composting.
Common Mistakes to Avoid
Even though a diy composting toilet with urine diverter is a fairly straightforward project, there are a few ways to mess it up.
First, don't skimp on the seal. If your box isn't relatively airtight (except for the vent and the fan), the fan won't be as effective at pulling odors out.
Second, make sure your diverter is positioned correctly. It needs to be far enough forward to catch everything, but not so far that it gets in the way of the solids bucket. It's a bit of a balancing act, so do a few "dry runs" (pun intended) before you screw everything down permanently.
Lastly, don't forget to tell your guests how to use it! A composting toilet requires a slightly different approach than a flush toilet. Sitting down for everything is usually the best policy to ensure the diverter does its job.
Wrapping It Up
Building your own diy composting toilet with urine diverter is one of those projects that feels a little daunting at first, but it's incredibly rewarding. There's a weird sense of freedom that comes from not being tied to a sewer line or a septic tank. Plus, you're doing something genuinely good for the planet by reducing water waste.
It's an affordable, practical solution that works just as well in a high-end tiny home as it does in a rustic hunting cabin. Once you get the airflow right and find a cover material you like, you'll probably wonder why we ever started using water to move our waste around in the first place. It's clean, it's quiet, and it's a total DIY win.