Bus Build: DIY Compost Toilet with Kildwick Separator – S03E25

After a couple trial vacations in an RV and Airstream with black tanks, we knew that was not the way we wanted to go and that a composting toilet would work best for our bus build.  When we glamped in our bus we simply used a bucket with peat moss.  It worked and was way less smelly than our black tank experiences.  However, we wanted something nicer for our conversion.

Spending $1000 on a composting toilet seemed like an unnecessary expense, so our aim was to make an affordable DIY toilet with the scrap wood we have lying around and repurposing what we could.  There was one important part of the puzzle  that we needed that would make all the difference - a urine separator or diverter. 

The Kildwick Klassik Separator was the key to making our dream throne! It diverts the pee forward into a bottle, or you can choose to divert it into a grey tank, and the poo into a bucket of peat moss/sawdust whatever alternative you want. It’s made of recyclable polystyrene making it easy to clean and Kildwick makes it all really easy for you with installation instructions and options to suit your needs.  

Composting toilets make a lot of sense to us.  We will save a lot of water this way and in the future when we find land and settle down we can make humanure for our fruit trees!  #dreamhome

We wanted to customize our toilet to fit our tiny bathroom design, however Kildwick offers a variety of options depending on your needs, desires and budget. You can buy a complete toilet, a DIY toilet with all the parts or just the parts you want/need. 

We made our wooden box with scrap plywood, although we curved the one corner as that side will be up against our hallway and we didn’t want to be bumping into a sharp corner accidentally.  Let’s face it, I’m a clutz, so we may as well prepare our tiny bathroom for it. We reused a plastic bucket that we buy our cat litter in to collect our solids, and made a little wooden frame to ensure the bucket didn’t slide around while we drive.  

We chose not to go with a bottle for the liquids.  I have seen a lot of travelers complain that the bottle fills up faster than you would expect and have seen some funny YouTube videos of people trying to get their urine bottle out when it’s overflowing.  Funny to watch but not funny to be that person! So instead, when we are ready to do our plumbing, we will divert our liquids to our grey tank. The bottle is an easy option if you want to forgo the plumbing though.

We also made a divider in the box which acts both as a brace/support (because you don’t want your throne to collapse in the middle of doing your business) and to separate the area we will store a bin of fresh peat moss (after you go #2 you simply scoop some fresh peat moss on top). 

Another little bonus we added to our toilet was a Gas Strut Lid Lift so that when we open our lid to add peat moss or change out the bucket of solids it will stay open by itself. 

OK now let’s talk about the paint, stains and varnish! 

We decorated the outside of our box with scraps from our ceiling planks that had holes/knots in the wood that weren’t going to work for our ceiling but would make a great feature on our toilet box. We painted them with chalk paint and distressed them for a shabby chic look. We are aiming to choose products that are non-toxic for our build wherever possible and ideally we would have used wax to seal these planks and the chalk paint.  We thought we had some leftover wax from previous projects but alas we could not find it. We did find a water based polycrylic in the house. We debated over this option for a while. Trying to use non-toxic products vs using what we have rather than buying new.  After some research we decided it had fairly low VOC’s (Volatile Organic Compounds) so using what we already had was best in this case. The Polycrylic is probably the best way to make the planks water resistant. The wax would be a good non-toxic way to go but would require re-coating every so often.

We painted the inside of our box with leftover Flex Seal (a non-toxic rubber coating) from our bathtub. There will be plumbing inside this box, so there is always the possibility of a leak at some point so we thought this was a good option to protect the wood and make clean ups easy. We did use a Rustoleum clear enamel coating over this to give it a smooth surface to wipe clean.  This is definitely not a non-toxic option but as we always say, we do the best we can to choose non-toxic options and this is one area I have not been able to find a non-toxic option.

We decided to go for a natural stain for our lid, we tried a few options:

1. Green tea, coconut oil and water
2. A mystery jar of stain mix Don’s cousin made, we think from the walnuts on the property
3. Rooibos tea, coconut oil and water

Rooibos tea was the winner for our bathroom!  It gave a light stain yet a warm honey feel to the wood.

To seal the wood and make it water resistant (we are in a bathroom after all) I spent some time researching non-toxic wood sealers. Traditional wood sealers are extremely high in VOC’s, in other words the harmful chemicals emitted during application (and possibly for a while afterwards). I found a great blog that reviewed different non-toxic wood sealers, they considered both how eco-friendly the product was plus how well it performed. 

This blog helped me pick Safecoat Polyureseal EXT as our wood sealer for the lid, and the rest of the toilet box (every side of the wood basically). To be honest Safecoat's website was confusing to me (as far as finding what I needed) but they were quick to respond and help me choose the right sealant for our project. We are very happy with the result so far.

Big thank you to Kildwick for partnering with us and sending us the Klassik Separator.  Our only expenses were:

Toilet Seat - $31.15

Gas Strut - $9.89

Paint - $35.99

Safecoat Wood Sealer - $46.70

Total: $123.73

The rest was all scrap and repurposed materials and there is plenty leftover paint and wood sealer for us to use on other furniture in the bus. Definitely worth the savings and we are thrilled with how it looks and feels to sit on.  The only added expenses down the line will be adding the plumbing to divert the liquids and fan to extract any possible smells. You could go cheaper with a DIY compost toilet, but we feel we got the best of both worlds - a very affordable throne!

Up Next
With the help of Don’s dad, a retired electrician, we set up our 12V wiring for our lights.

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