Building instructions for a composting toilet in a motorhome

Many of our portable toilet blog readers or people interested in portable toilets are often desperate for detailed instructions on how to build a portable toilet.

They often find themselves at a loss in their motorhome bathroom, which is made entirely of cohesive plastic. It is not immediately obvious how to attach them.

Adolf took the trouble to document such instructions for converting the cassette toilet and published them on his website:

He also allowed us to publish and link his construction manual of the composting toilet at As usual, we have linked all the products mentioned.

Starting point

The shower tray in the Concorde motorhome was in need of repair. Adolf had been thinking about a composting toilet for some time, so he took advantage of the situation to convert the motorhome bathroom, including the cassette toilet.

To do this, he studied numerous videos and articles in order to deal extensively with the construction of a composting toilet.

A large bench toilet was installed in the Concorde motorhome, which took up a lot of space, as did the washbasin construction. The conversion was intended to free up a lot of space.

The idea was to continue using the existing service flap for removing the urine and solids tank. The existing power connection for flushing the old Thetford cassette and the SOG system were later to be used for the composting toilet.

Construction manual composting toilet

1. Removal of cassette toilet

First, the screws of the cassette toilet have to be found. Adolf looked at countless instructions on the internet to find out where to look for the screws.

Here we would like to refer to the article by Jonas, who took photos. You can find the link below this paragraph.

He located the screws in the cassette compartment. He also gave the hint that some bench toilets are additionally held with hooks in the rear area. Therefore, it makes sense to first lift the bench toilet upwards.

A small tip: remove the silicone joints beforehand and disconnect the water and electricity lines. Adolf was surprised how easy this work was.