KAKAPO©   Composting Toilets

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Kakapo composting toilets have been designed for ease of installation into both new and existing buildings.

A common feature of other composting toilets is the need for either a substantial sub floor space or a highly raised floor of the toilet room to accommodate the collection chamber.

By employing a rotating drum in a horizontal position, the need for this vertical space has been greatly reduced, making the Kakapo composting toilet suitable for buildings with a low floor heightincluding those with a concrete slab floor.

The total height of the unit is 750mm. The standard seat height of a conventional toilet is 400mm. If this standard height is desired, a recess of 350mm will need to be created for the unit to sit in - a simple matter when constructing a new building. See the accompanying diagrams for the necessary dimensions.

If retro fitting to an existing building with wooden floor and pile construction, some modification will be required to the sub floor framing and extra piles may be required where spanning members such as bearers or joists are cut. A firm support such as a concrete slab or timber deck (650mm x 1430mm) will also be required to sit the unit on.

If retro fitting to a building with a concrete slab floor, the unit is simply placed directly on the floor and a small step is positioned in front of the unit. Alternatively, the surrounding floor may be built up to the desired height..

It is desirable that the bottom of the unit be at least 50mm above finished ground level - and certainly not below ground level, unless protected from possible flooding.

The unit comes with two wall flashing pieces that seal the unit from the elements on the outside and provide a smooth finish to the internal lining. These pieces will fit anywhere along the length of the unit thus allowing for walls of any thickness up to 500mm. The external flashing is placed beneath the wall cladding and is left loose until the toilet unit is in place. This enables the building to be clad and construction to proceed without the need to have the actual toilet installed thus reducing the risk of damage to the unit.

A coved moulding is also provided to finish the unit where it meets the floor or alternatively this may be finished with a timber surround.


Venting of the unit is best achieved with a simple 100mm vent pipe, placed directly behind the toilet seat, passing straight up through the roof above with a minimum height of 4.5 metres. The unit is supplied with a standard 100mm waste pipe socket for this purpose positioned directly behind the seat. The natural chimney effect of the vent pipe ensures that a small amount of air is constantly being drawn in through the toilet seat, from the surrounding room and thus maintains odour free operation.

If it is not possible to vent internally, the unit can also be vented from the outside of the building. In this case a small fan may need to be placed in the vent pipe to maintain an adequate airflow especially during cold weather. Because the fan itself will obstruct the vent pipe, natural convection will be impeded and therefore it will need to operate continuously. Advantages of using a fan is that bends may be placed in the vent pipe, the roof penetration can be avoided and a shorter pipe can be used (1200mm above the roof height)

A vent top diffuser should be employed in either case to minimise down-draughts and this can also be supplied.

The vent pipe should be firmly fixed to framing members above the unit so the unit itself is not taking the full weight of the pipe. Bracing of the pipe to the roof will also be required and this can be done by way of guy wires or bracing rods.


A family of two adults and a couple of kids will produce approximately 4 litres of liquid per day. Some of this will be absorbed and evaporated within the toilet. - the rest will drain from the unit- as you can see, not a great quantity.

The position of the drip tray drainage sump is shown on the accompanying diagram. The most convenient method is to set a 40mm waste pipe into the support slab (see detail) which corresponds to the drain hole in the bottom of the unit with a drain pipe leading to the desired collection or disposal system. The outlet from the drip tray is then turned to the down position so liquid will flow directly into the drain pipe. If the unit is supported on a timber platform, ensure that the area around the drain is free of structural members such as joists or bearers so as not to conflict with the drain.

If installing fully inside a building with a concrete floor and a drain cannot be provided in the slab, sufficient space for a drain will need to be created by supporting the unit on a 100mm high timber frame which should extend fully around the perimeter of the unit with at least two cross members. The drain pipe will then pass horizontally through this frame and away to disposal.

Excess liquid can be disposed of in a simple soakage sump, run to an existing septic tank or grey water system. On the other hand, this high nutrient fertiliser can be collected and used to great benefit on appropriate crops such as citrus or other fruit trees.

Click here for dimensioned plans

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