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pic=Twin_pits_for_pour_flush.png|
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Input1=Blackwater|Input2=Greywater |Input3=Anal cleansing water| Input4= |Input5=|Output1=Compost - EcoHumusPit Humus| Output2= | Output3= | Output4= | Output5=
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[[Image:Icon_twin_pits_for_pour_flush.png |right|95px80px]]'''This technology consists of two alternating pits connected to a [Pour Flush ToiletPour Flush Toilet] (U.4). The blackwater (and in some cases greywater) is collected in the pits and allowed to slowly infiltrate into the surrounding soil. With Over time, the solids are sufficiently dewatered and can be manually removed with a shovel.'''
The superstructure, toilet and twin pits, for the Twin Pits with Pour Flush pour flush technology can be designed in various ways: ; the toilet can be located directly over the pits or at a distance from the pitsthem. The superstructure can be permanently constructed over both pits or it can move from side to side depending on which pit one is in use. No matter how the system is designed, only one pit is used at a time. In this wayWhile one pit is filling, a continuous cycle of alternating pits means that they can be used indefinitelythe other full pit is resting.
===Design Considerations=== The difference between this technology and the [[Double Ventilated Improved Pit|Double VIP]] pits should be of an adequate size to accommodate a volume of waste generated over one or [[Fossa Alterna]] is that it two years. This allows for the addition contents of water and does not include the addition of full pit enough time to transform into a partially sanitized, soil or organic -like materialthat can be manually excavated. As this It is a water-based (wet) technology, recommended that the full twin pits require a longer retention time be constructed 1 m apart from each other to degrade minimize cross-contamination between the material before maturing pit and the one in use. It is also recommended that the pits be constructed over 1 m from any structural foundation as leachate can be excavated safelynegatively impact structural supports. Water within the pit can impact its stability. A retention time Therefore, the full depth of 2 years is recommended. The degraded material is too solid the pit walls should be lined to prevent collapse and the top 30 cm should be removed with a vacuum truckfully mortared to prevent direct infiltration and to support the superstructure.
Alternatively, the Pour Flush Toilet could also be directly connected to the pit in use by a single straight pipe fixed in place with light mortar and covered with earth. The risk of failure and misuse is minimized by ensuring that the junction and pipes are not easily accessible.
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- Can be built and repaired with locally available materials. <br> - Because double pits are used alternately, their life is virtually unlimited. <br> - Excavation of humus is easier than faecal sludge <br> - Potential for use of stored faecal material as soil conditioner. <br> - Flies and odours are significantly reduced (compared to non-ventilated pitswithout a water seal). <br> - Suitable for all types of user (sitters, squatters, washers and wipers). <br> - Low (but variable) capital costs depending on materials; no or low operating costs if self-emptied. <br> - Moderate Small land area required<br>- Significant reduction in pathogens. | con=- Excreta require manual Manual removal. of humus is required<br> - Clogging is frequent when bulky cleansing materials are used<br>- Higher risk of groundwater contamination due to more leachate than with waterless systems
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==Adequacy=Appropriateness=== The Twin Pits with Pour Flush is pits for pour flush are a permanent technology that is appropriate for areas where it is not appropriate possible to continuously move a build new pit latrinelatrines. It As long as water is a water-based available, this technology and is only appropriate where there for almost every type of housing density. However, too many wet pits in a small area is a constant supply not recommended as the soil matrix may not be of sufficient capacity to absorb all the liquid and the ground could become water for flushing -logged (e.g. recycled greywater or rainwateroversaturated). Greywater can be co-managed along with In order for the blackwater in pits to drain properly, the twin pitssoil must have a good absorptive capacity; clay, tightly packed or rocky soils are not appropriate.
This technology is not appropriate suitable for areas with a high groundwater table or areas that are frequently floodedwhere there is frequent flooding. In order for Greywater can be co-managed along with the blackwater in the twin pits , especially if the greywater quantities are relatively small, and no other management system is in place to drain properlycontrol it. However, large quantities of flushwater and/or greywater may result in excessive leaching from the pit and possibly groundwater contamination. The dewatered, solid material is manually emptied from the soil must have a good absorptive capacity; claypits (it is dug, not pumped out), therefore, tightly packed or rocky soils are space is not appropriaterequired for vacuum trucks to access them.
===Operation & Maintenance===The Twin Pits with Pour Flush technology will only work properly if pits must be regularly emptied (after the recommended two pits are used sequentially year resting time), and care must be taken to ensure that they do not concurrentlyflood during rainy seasons. Therefore, an adequate cover for the out of service pit Emptying is requireddone manually using long handled shovels and proper personal protection.
==Health Aspects/Acceptance= Sulabh toilets=== The Indian NGO [http://www.sulabhinternational.org/ Sulabh International] designed a [https://www.ircwash.org/sites/default/files/323.1-1299.pdf system] using pour flush toilets and twin pits for treatment of sanitation products. They have constructed over a million toilets in India. They further designed a system which converts the effluent into biogas. These technologies are now used by 10 million people in rural India. This contributed greatly to the increase in number of people using a toilet, from 27% to 59% in the last 5 years. They have also built public toilets in Afghanistan, Bhutan, Ghana, Ethiopia, Madagascar, Mozambique, Laos, and Cambodia. They are planning to start up Sulabh Sanitation centres in 50 more countries soon.
* Latrine leachate can contaminate groundwater; * Stagnant water in pits may promote insect breeding; * Pits are susceptible to failureMara, D. D. (1985). [https:/overflowing during floods/sswm.info/sites/default/files/reference_attachments/MARA%201985%20The%20Design%20of%20Pour%20Flush%20Latrines_0.pdf The Design of Pour-Flush Latrines]. UNDP Interregional Project INT/81/047, The World Bank and UNDP, Washington, D.C., US.
===Acknowledgements===
{{:Acknowledgements Sanitation}}