In a UDDT, the urine is kept separate and drained via a basin with a small hole near the front of the toilet bowl or squatting pan, while feces fall through a larger drop-hole at the rear.

[7] Designers and users of UDDTs should strive to keep the feces pile as dry as possible, as this is the most important factor in the prevention of odor and flies.

During storage, the feces’ natural moisture slowly evaporates and exits via the vault's ventilation system, or is absorbed by the dry cover material.

[4]: 3  The main ones - which distinguish a UDDT from a pit latrine - are the urine diversion toilet seat or squatting pan, and one or two feces vaults (above ground).

The UDDT system was accompanied by greywater treatment facilities, solid waste composting and the reuse of these materials as a fertilizer in agriculture.

However, due to several problems related to improper design and installation, the lack of a cohesive plan to address these deficiencies and the resulting resident objections, the UDDTs were replaced by conventional flush toilets in 2009.

Likewise, installation is a relatively simple process given that everything needed for the proper functioning of the toilet, except a source of electrical power for those models that include a fan and some allowance for exterior ventilation, is contained within the molded or wooden carcass.

For most UDDT types, users are encouraged to add a handful or scoopful of dry cover material directly after each defecation event.

This cover material is added to promote dry conditions in the feces vault (by absorbing moisture), to control odor, to prevent infestation by flies and to create a visual barrier for the next user.

In scenarios wherein excreta is to be reused in agriculture, a secondary treatment of fecal matter and storage of urine is advisable to ensure adequate sanitization.

If the dried feces are not reused in agriculture they can instead be buried at a minimum depth of 25 cm in which case they normally do not pose a public health risk.

Urine that leaves the body of a healthy person is close to being sterile and requires much less treatment for pathogen removal than feces or fecal sludge.

Urine from the UDDTs can safely be used as nitrogen-rich and phosphorus and potassium containing fertilizer after a recommended storage period for pathogen reduction (see above under "Further Treatment").

A well-maintained UDDT is an odor and insect free toilet which is appreciated by users and allows simple removal and far less offensive and safer handling of the fecal material once the feces vault has filled up.

Moreover, the risk of water pollution is minimised through the safe containment of feces in above-ground vaults and this allows the toilets to be constructed in locations where pit-based systems are not appropriate.

However, the installation of UDDTs in all households connected to a common sewer would result in vastly reduced volumes of water, nutrients and organic matter that arrive at the associated wastewater treatment plant.

Sewer-based excreta management is impractical in many regions due to limited water supplies and the high cost of sewer systems and wastewater treatment plants.

The separate, waterless collection and treatment of urine and feces in UDDTs prevents hormones, pharmaceutical residues and other micropollutants which are contained in human excreta from entering surface water or groundwater via treated sewage.

[22] This is because in conventional sewage treatment plants, these micropollutants are only partially removed and the remainder is discharged into surface water, possibly reaching the groundwater.

[36] By not mixing human excreta with water and the other contaminants that are disposed of in sewers and septic tanks, UDDTs avoid many of the problems associated with these practices.

[37] When a period of for example 10 years is considered, UDDTs may well be the more economical alternative, since the emptying of feces vaults is simple and safer, thus less expensive, even if users decide to enter into a contract with someone else to do this.

However, to enable accurate comparisons of costs, this needs to be assessed on a case-by-case basis because the sewer system and treatment plant also transports and treats greywater whereas the UDDT does not.

[15] The UDDTs with two dehydration vaults that are known today were originally designed around 1950 in Japan and further developed in Vietnam in the 1960s as a means of increasing the hygienic safety of excreta reused in agriculture.

[39] This means their development was originally closely linked to the ecosan (ecological sanitation) approach to optimizing resource recovery of nutrients and organic matter in agriculture.

Prefabricated ceramic or plastic urine diversion squatting pans and pedestals have become available on the market, generally increasing the durability and perceived prestige associated with the system.

[20] Numerous off-the shelf commercial products are now available and are used in locations where a connection to a sanitary sewer system is not possible, permitted or desired such as in remote summer cottages or for camping activities.

In most cases, these UDDTs utilize soak pits (normally located directly beneath the toilet superstructure) for onsite disposal of urine.

The compost produced at these facilities is sold to farmers, organizations, businesses, and institutions around the country to help finance SOIL's waste treatment operations.

In these regions, piped water supply is often lacking, clay-rich soils do not permit infiltration of wastewater, and the groundwater level is usually high.

For instance: For dry toilet users in the United States (which includes users of UDDTs), an important distinction to keep in mind—and one that is supported by the aforementioned existence of numerous state regulations which make no mention of, and also diverge widely from, the requirements of the federal regulations that govern the management of sewage sludge—is that as long as the excreta in question is not ever referred to as "fertilizer" (but instead simply a material that is being disposed of) the federal 503 rule, known colloquially as the "EPA Biosolids Rule" or the "EPA Sludge Rule", has no jurisdiction over the byproducts of a dry toilet and that all oversight of these materials falls to the individual states.