Applications for Non-Water-Based Toilets

Customers curious about nonflush toilets need to know they require careful selection and meticulous maintenance before making a change

Applications for Non-Water-Based Toilets

There are several types of nonflush toilets, based on the goals of water conservation or functioning when a water supply is not available. There are many primitive cabins without running water that need a method to deal with human toilet waste. Non-water-based toilets are also used with graywater systems to reduce, but not eliminate, the solids and bacteria load in the wastewater generated in the structure. The two most common nonflush toilets are discussed below.

Composting toilet

Waterless and forced-air composting toilets produce compost (which is still considered septage). Some models use a very small amount of water or a chemical foam to assist the passage of waste to the composting chamber. A composting toilet is a self-contained unit (not connected to a septic or sewer system) that breaks down, reduces the volume and dehydrates human waste to compost. Sometimes the kitchen waste is composted in the unit as well. Toilets may be large- or small-capacity units. Careful consideration must be given to select the appropriate model and size for a specific application. If larger units are to be used, they are usually installed as part of a building’s construction. Some of the units are relatively small and are self-contained. Others have big chambers under the toilet, requiring space in a basement or crawl space.

The toilet will consist of a place to sit (which is likely to look a lot like any other toilet), a composting chamber that breaks down and sanitizes the sewage, and a drying chamber or tray that permits moisture to escape, reducing the sewage volume. The toilets contain mechanical agitators, thermostats, humidistats, heaters and fans to assure the proper moisture content and temperature are maintained. Often some sort of bulking agent such as sawdust is added into the composting unit to reduce odors, creating air gaps for aerobic bacteria to break down the material. 

Microorganisms living in the compost break down much of the waste. For seasonal facilities, having a stable community of microorganisms can be challenging due to the inconsistent food source. In some jurisdictions, the local plumbing code may not recognize composting toilets as an approved fixture and therefore may have limited application. Some manufactured composting toilets are certified by NSF, which makes them easier to be accepted by health and building departments. 

Composting toilets come in models that use little water or no water at all, and in electric (heated and power-vented) models and nonelectric models. Some models include electromechanical mixers that mix waste in with a mulch product to speed and improve the composting process. Properly designed and installed, the toilet is vented so there are no abnormal toilet odors. Periodically the compost must be emptied, and on occasion toilet components are cleaned. The waste from a composting toilet is considered septage and must be treated properly. 

People use the toilet in a normal manner, and modern composting toilets in fact look familiar, resembling water-based toilets in general shape and comfort. Waste is mixed with a “starter mulch” to begin the composting process. Composted waste is emptied from the toilet at intervals ranging from one or two months to 12 months, depending on level of use and toilet design. Composting toilets that do not mix new human waste with material already being composted produce a compost that is easier and safer to handle. This is a reason that some models use multiple containers or compartments, though there are other solutions to this problem. If the visible portions of the toilet need cleaning, normal household cleaner and toilet brush are used.

Direct homeowner involvement in the operation, monitoring and maintenance of the toilet is required, even if a management structure exists to provide ongoing system monitoring and maintenance. This involvement includes monitoring moisture content, control of flies, periodic mixing of the composting material, and periodic removal and proper disposal of the composted material following the Environmental Protection Agency federal 503 regulations. The composting waste from homeowner-managed systems cannot be simply used as compost in the yard due to less than optimum conditions and lack of monitoring.

Incinerating toilet

An incinerating toilet reduces human excreta and urine to ash and vapor by incineration. This toilet only handles blackwater and is not designed for any water-carried sewage. This process is fueled by natural gas or electricity. Careful consideration must be given to select the appropriate model and size for a specific application. As this process only handles blackwater, a system providing treatment and dispersal for the graywater is necessary. This blackwater handling process is located inside a residence. This option requires the use of a bowl liner and/or other methods specified by the manufacturer to keep the toilet bowl clean. There are gases that must be properly ventilated. Residual ash must be taken from the toilet and disposed of properly. Operation of the toilet (i.e., use of a liner and activating the burning cycle) is unfamiliar to the public and, therefore, may not be appropriate for public access restrooms.

Although most property owners have water-based flush toilets, options exist to reduce their water usage, reuse their graywater or have facilities when water is not available. These systems need management for proper operation and protection of public health and the environment.

About the author
Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation, and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association and the National Onsite Wastewater Recycling Association, and she serves on the NSF International Committee on Wastewater Treatment Systems. Ask Heger questions about septic system maintenance and operation by sending an email to


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