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close this bookSanitation Promotion (SIDA - SDC - WSSCC - WHO, 1998, 292 p.)
close this folderPromotion through innovation
close this folderInnovative technologies
View the documentTowards an ecological approach to sanitation - Uno Winblad1
View the documentPromoting composting toilets for Pacific Islands - Leonie Crennan1
View the documentPeri-urban sanitation promotion in Mozambique - Darren Saywell1
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View the documentExperimenting with dry toilets in El Salvador - Ron Sawyer1 and George Anna Clark2
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View the documentLow-cost sewerage - Duncan Mara1
View the documentWorm composting and vermitechnologies applicable to sanitation - S. Zorba Frankel1

Experimenting with dry toilets in El Salvador - Ron Sawyer1 and George Anna Clark2

1 SARAR TransformaciC, Mexico.
2 Espacio de Salud, AC, Mexico.

A successful solution to an environmental challenge

Environmental factors, including a chronic water shortage, and high groundwater in parts of the country have made it necessary to adopt drastic measures in El Salvador. Increasing priority is being given to constructing dry toilets, which require no water for the disposal of human waste and, when properly maintained, represent a safe, sustainable alternative for family sanitation. Committed NGOs, the Ministry of Health and the Social Investment Fund, with the financial and technical support of UNICEF, USAID, and Sida have constituted a strategic alliance to bring this appropriate technology to E Salvador. This technology is being replicated, adapted, and sustained on a large scale. A comprehensive educational strategy that integrates the construction, use, and management of dry toilets with personal hygiene and ecological sanitation is a key component of the programme.

Programme description

Environmental factors in El Salvador have made it necessary for the country to adopt extreme measures for improving its sanitation coverage. A chronic water shortage in much of the country has made conventional water-borne sewerage unrealistic, while the high water table characteristic of much of the coastal area of El Salvador makes traditional pit latrines virtually unthinkable. One significant change has been the increased priority given to the construction of dry toilets, which require no water for the disposal of human waste, while the use of impermeable above-ground chambers prevent the contamination of sub-surface water.

A growing awareness of environmental problems and the commitment of NGOs, the Ministry of Health and the Social Investment Fund, together with financial and technical support from UNICEF and USAID, have helped to bring the modified Vietnamese double-vault toilet to El Salvador. As a result of experiments and evolving government policies, this appropriate technology is being replicated and sustained on a large scale. With approximately 100 000 of these dry toilets and an ongoing research and development programme funded by UNICEF and Sida, this Central American country is rapidly becoming a world leader in sanitation without water.

The dry toilet

The dry toilet relies on a special toilet bowl that diverts the urine to an absorption pit or to a container where it is collected for use as fertilizer. The faeces fall into the chamber below the toilet and are dehydrated to destroy pathogenic organisms, so that the substance can be reused as a fertilizer and soil conditioner.

The maintenance of the system involves a set of simple activities. After defecating, the user sprinkles dry materials such as ashes or lime (or a mixture of dry soil or sawdust with ash or lime) over the faeces. Every week the contents of the chamber should be stirred with a stick and more dry material added.

The separation of urine from faeces and the addition of dry material, reduce unpleasant odours and flies, which are serious problems of traditional latrines. The toilet's double chamber allows the contents on one side to lie idle, while the family continues to use the other side. Under normal circumstances the chamber in use fills up in not less than six months, which is enough time to assure that the material in the other chamber has dried adequately. By drying the faecal material for at least six months, even the most long-lived pathogens will be destroyed, leaving an innocuous material that can be removed and disposed of or reused as a soil conditioner.

Pathogen destruction

To properly use and maintain a dry toilet, it is useful to understand how and why the system works. Whereas the term “dry sanitation” can refer to either dehydration or decomposition, it is helpful to appreciate the basic differences between the two processes.

Dehydration means that the humidity of the contents of the vault is brought down to below 20 per cent. For effective composting, humidity must be kept above 60 per cent. In a dehydrating system, pathogens are destroyed by depriving them of water and by increasing the pH above tolerable levels. Users help the process by adding dry materials and lime (or ash) as part of routine management.

The humidity interval of 20-60 per cent should be avoided, because it results in incomplete dehydration, malodorous decomposition and fly breeding.

Dry toilet cycle.

Source: Redrawn from Letrinas secas: una polca nacional en El Salvador and Saneamiento sin agua, El Manantial. Boletde la Red Regional de Agua y Saneamiento para Centroamca (RRAS-CA), A, # 1, August 1996.

Begin use

You must empty the urine receptacle regularly

When the first chamber gets full, you move the toilet bowl to the second chamber

While the second chamber is filling, the first one is decomposing

Once the second chamber is full, you empty the first one, and you move the toilet bowl again

The cycle begins again

Figure 2. The double-vault (LASF) toilet

Source: Cr Ae, Helechos No. 5, Col. Jacarandas, CP 62420, CuernavacMorelos, Mexico.

Had these critical facts been better understood by many sanitation pilot projects worldwide, many unfortunate failures could have been avoided and the unjustifiable mistrust of dry sanitation technology much more quickly overcome.


Education and mobilization

UNICEF has played a vital role in developing an educational approach that integrates the social and technical aspects of dry sanitation. Initially, the focus was at the family level, involving household visits by trained community promoters (visitadoras), who follow a programmed sequence of learning modules. This has been complemented by regular monitoring of key aspects of individual and family hygiene, as well as toilet use and maintenance.

In 1996, to get communities more involved in the water and sanitation programmes, SARAR TransformaciC provided training in participatory methods (including PHAST) to technical and field staff of key NGOs, the Ministry of Health, and UNICEF. The comprehensive educational strategy, which integrates the construction, use, and management of dry toilets with personal hygiene and ecological sanitation is proving to be critical for promoting the acceptance and sustainability of alternative sanitation approaches. An important result of this participatory learning process has been the consolidation of an inter-institutional team of trainers sponsored by UNICEF. These trainers, promoting participatory methods, train staff from other institutions and other sectors, and adapt and produce non-directive learning materials.

Three very different experiences are discussed below to illustrate the significant learning that is taking place in El Salvador.

Hermosa Provincia. After one child fell into a pit latrine, the Hermosa Provincia peri-urban neighbourhood in the capital city of San Salvador was motivated to build a dry sanitation system. As a result of intensive education in using and maintaining the dry toilets provided by the Ministry of Health, plus effective community organization and follow-up support from a local church, the 130 units in this community have been functioning successfully over the past six years. Although most of the toilets are actually built into the houses, there are no unpleasant odours, nor any flies. After a year, the dehydrated material is removed from the chamber and is used in a communal nursery, occasionally sold (at US$ 4.65 per 100 kg), or used as landfill on a nearby site belonging to the church.

Figure 3. Constructing a double-vault, desiccating toilet with urine separation

Source: Uno Winblad, Pataholm 5503, 38492 em, Sweden.

Tan. The Ministry of Health, with technical support from UNICEF and SANRES (see Box 1) is developing and testing experimental solar-heated toilets, with urine diversion in the semi-rural village of Tan. Unlike most other dry toilets, this type of solar toilet has just one chamber and uses solar energy to accelerate the desiccation process. Built entirely above ground, the 36 experimental units include urine diversion, and produce a dry product from the human faeces that can be safely used after storage of at least six months.

Box 1. SANRES Project3

SANRES (Sanitation Research) is a Sida-funded project that has been supporting dry sanitation research and development activities in El Salvador since 1994. The SANRES project is currently active in seven countries (Bolivia, China, El Salvador, Guatemala, Mexico, South Africa, and Vietnam) and has created an informal network in 20 countries. SANRES holds that any intervention in sanitation must take into account that sanitation is a system including the natural environment; society (with its beliefs, values, practices, technologies); a device (the physical structure that receives the human excreta; and processes (the physical, chemical, and biological processes, such as dehydration or decomposition, that take place inside the device). Unless each of the system's elements is considered with equal rigour, effective and sustainable intervention will be difficult to achieve.

3 For more information, contact Uno Winblad, SANRES, fax: +46 499 24253 or email:

The Tan toilets produce no flies or odours, but do require that the user shifts the pile under the toilet seat to the back of the chamber every one or two weeks. On some units, a mechanical “pusher” is used to shift the pile without opening the chamber. Because of the chamber's limited size, the material at the rear of the chamber must then be emptied every second or third month, to be stored until disposed of or used in the garden as a soil conditioner or fertilizer, composted or used as the drying agent in the toilet.

This project is demonstrating that the size of the dry toilet can be significantly reduced (the volume of the chamber has varied from 0.35 to 0.6 m3), thus lowering the cost of construction materials. The direct cost (materials and labour only) of a solar toilet is US$ 225, compared to US$ 271 for a standard dry toilet. Space requirements have also been reduced significantly, which is a very important consideration in highly dense urban areas.

Studies are being conducted to reduce maintenance needs to a minimum while still assuring an acceptable level of pathogen destruction, before promoting and constructing solar toilets on a large scale. In addition, the project is continuing to experiment with optimal design and location. The 36 units now in use are being expanded to 500 units to test the applicability of the system on a larger scale. This next research phase will concentrate on the sociocultural issues (user education and training, extension support) associated with safe, sustainable use.

Chicuma. ProVida, an innovative national NGO, supported by UNICEF, has introduced a change to the traditional pit toilets in the rural community of Chicuma, inhabited by former guerrillas. In an otherwise traditional 1.5-2 m deep pit toilet, faeces and urine are kept apart by using the urine-diverting seat.

Over two years ago, about 70 families installed the seats for urine diversion, while a few households built traditional toilets. The latter continue to have odour, fly, and mosquito problems, while the former generally do not. Only during the rainy season, and only for a short period of time, when there is an increase of humidity in the otherwise dry pit, do flies and odour become a nuisance in the modified toilets. It has been observed that the depth of the pit in the modified toilet can be reduced. Overall the community is very satisfied with this innovative pit toilet, which is seen as a positive first step towards gradually introducing the standard dry toilet.

Although evaluations and additional technical studies (for example, on the die-off rate for pathogens and parasites) are necessary, El Salvador's experiences with dry toilets corroborate several basic sanitation principles. As with any sanitation system, to be safe and environmentally sound, dry toilet programmes require a clear understanding of the technology to be used and the prevailing natural conditions. Community organization and education are important components to assure the system's sustainability. Since the family must undertake more maintenance than required for traditional toilets. But wherever these conditions are met, dry toilets have proved to be a sustainable solution for family sanitation.

Key institutions and responsible persons

Jean Gough
WATSAN Project Officer
Apartado Postal 1114
San Salvador, El Salvador
Tel: +503 263 3380
Fax: +503 263 3385

Uno Winblad
SANRES Coordinator
Pataholm 5503
S-38492 em, Sweden
Tel: +46 499 24255
Fax: +46 499 24253

References consulted

Brand T. Letrinas secas: una polca nacional en El Salvador and Saneamiento sin agua, El Manantial - Boletde la Red Regional de Agua y Saneamiento para Centroamca (RRASCA), A, # 1, August 1996.

Winblad U, Dudley E. Dry toilets for urban areas: the findings of the second SANRES workshop. Mexico City, November 23-26, 1994.

Report for consideration at the El Salvador Meeting. Meeting of the Water Supply and Sanitation Collaborative Council, 25-29 March 1996, El Salvador.