Construction of a composting toilet with external urine divider a self-built wooden caravan

Peter sits in front of the self-built caravan. He built it himself from wood and it also has a composting toilet.

An impressive achievement - we have to state. In addition to the photos, Peter has also written something about the construction of the composting toilet. He came up with a special feature during the construction.

Construction composting toilet - special feature

Peter wrote: The toilet lid including separator/ divider can be removed upwards.

A commercially available siphon is mounted underneath in the cavity into which the outlet of the urine separator automatically protrudes when the lid is closed.

Bau Trenntoilette
Bau Trenntoilette

So there is no need to connect a hose or similar. To ensure that the trap is always filled with water (and not only with urine = odour) after using the toilet, the waste water hose of the washbasin leads laterally into the washing machine connection of the trap.

When washing hands after using the toilet, the trap is automatically filled with water. Urine and waste water are fed together into a 35-litre tank under the caravan. This in turn can be emptied into the sewer via a drain cock.

Peter writes about this: Has proven to be a clean and really almost odourless version.

Further construction measures Separating toilet

At the bottom of the separator I have attached a simple rectangular bucket with a hinged lid using two rotating wooden toggles. We put a poop bag in it, which we can then remove cleanly and usually dispose of every 2-3 days.

The bucket can be easily removed for cleaning. Because there was still space underneath, there is a plastic box as a reserve container for the sawdust.

Odour nuisance due to cassette toilet

We had a chemical toilet in our previous caravan. The smell when using and emptying it was much greater and more "disgusting" than with our current dry toilet!

With your separator, the wonderfully warm polystyrene toilet lid and a little wood/material, you can really build a very good alternative to the expensive and environmentally harmful chemical toilets very cheaply.

If you want to know which reasons speak for a change, read our article here:

Bau Trenntoilette

Why the change from a cassette toilet to a composting toilet is worthwhile

Peter's construction tip

Perhaps another idea for other fitters: The door to the "bathroom" is hinged twice. When closed, no unused space is lost. When open, it swings forward and, together with the adjacent cupboard door, provides sufficient "foot space".

Since the caravan has a pop-up roof (it fits into our normal garage), the "bathroom" is closed upwards by means of two flaps.

The caravan body sits as a "load" on an aluminium platform trailer and can be removed from the trailer by means of 4 crank supports. I can also use the trailer separately.

Bau Trenntoilette

Impressions of the interior of the caravan

Wohnwagen Innen
Wohnwagen Innen

Materials for the construction of the composting toilet

  • Separating insert Privy 500
  • Stainless steel siphon
  • rectangular bucket for solids
  • 35 l urine tank
  • Wood for the cabinet according to personal preference


Peter decided here to build the composting toilet for external urine drainage. For this, he came up with a rather clever solution that also works well, as he himself writes.

A siphon takes over the task of the odour trap. Whenever external urine drainage is preferred, an odour trap should be installed.

As a rule, wastewater and urine are mixed, for example in the greywater tank. Mixing with water or longer collection times of urine lead to the formation of odours as the urine begins to decompose.

Therefore, we always recommend integrating an odour trap in such constructions.

We are also interested in your self-construction! Do not hesitate to contact us:

We look forward to receiving your e-mail!

These are our most popular construction sets for a composting toilet