Users' opinions

usually surrounded by many trees,which impede the airflow. This prob-lem cannot be easily overcome becauselocal people are obviously reluctant tocut down the trees which provide theannual harvests and are a valuablesource of income.

VIP latrines: are they always the bestalternative?by Patrick GossA sanitation study in Sierra Leone remindsworkers that VIP latrines need certain conditionsto function properly, and that where thoseconditions are not right alternatives must befound.

The airflow through the superstructure and up the vent-pipe was measuredwith the aid of a Draeger smoke puffer: 20 puffs were released into the pitjust below the squathole, and the time taken for the smoke to emerge fromthe vent-pipe was recorded. The number of flies were observed both in thesuperstructure and at the top of the vent-pipe. A subjective measurementwas used to record odours.

Various factors were thought to be capable of affecting the findings of oneor more of the measurements above. These include:o the siting;o the amount of wind and its direction (this involved releasing a few puffs

of smoke into the atmosphere and observing its rate and direction ofdispersion);

o the existence of a door;o alterations made to the design;o the height of the vent-pipe in relation to the height of the roof;o the length of time the latrine has been used; ando the amount of light entering the superstructure.

It should be noted that the results of the test when subjected to statisticalanalysis have relatively high standard deviations. (More details of the testsare available directly from the author, on request.)

IN SIERRA LEONE, as in many otherAfrican countries, Ventilated ImprovedPit latrines (VIPs) are very popular.They are commonly built by the villag-ers, often with the assistance of person-nel from both aid and local organiza-tions. But are VIPs the best option?This research, sponsored by WaterAid,evaluated the performance of VIPs andgathered users' opinions of them.

The VIP latrine was developed byPeter Morgan and Ephraim Chim-bunde nearly 20 years ago, and is animprovement to the traditional pitlatrine because, among other things, itis equipped with a ventilation pipewhich is capped with a fly screen. Thevent-pipe is designed to reduce signifi-cantly the odours and flies synony-mous with many standard pit latrines.Air movement across the top of thevent-pipe causes an updraught in thepipe from the pit. The air is sucked outof the pipe by air passing across thetop, and is replaced by new air whichis sucked in through the squathole inthe cover slab. The odours from the pitpass up the vent-pipe and disperse intothe atmosphere. Peter Morgan specifi-cally recommends that VIP latrines belocated away from trees, overhangingbranches, and anything else that mightimpede the action of wind across thetop of the different vent-pipe.

Flies in the pit are attracted to thelight from the vent-pipe. They fly upthe vent-pipe but are prevented fromescaping by the fly screen, and soon dieof dehydration and fall back into the pit.The inside of the superstructure shouldbe relatively dark so that flies are notattracted to light from the squathole.(Ryan and Mara give recommenda-tions regarding different vent-pipe de-signs.)

Various tests were conducted on thevent-pipes of VIPs in order to assesstheir efficiency in controlling odoursand flies (see box).

The results of the tests indicate that

Patrick Goss is National Maintenance Engineer,Lesotho Village Water Supply Section, P.O. Box269, Maseru 100, Lesotho.

the vent-pipe cannot operate efficientlyin many of the latrines. One of themain reasons for this is the shortageof land in Sierra Leone, where villagestend to be sited in forest clearings.There is little land available for VIPlatrines in the centre of villages be-cause of the necessity to site them atleast 15 metres from a cooking area.VIP latrines therefore tend to bepositioned on the outskirts and are

A questionnaire was designed, andvarious complaints about the VIPlatrine emerged: flies, odours, andmosquitoes were common objections.Many villagers did not like using thelatrines because they are dark. Mosthouseholders prefer a latrine with adoor, which they can lock to preventneighbours using them. WaterAid ac-commodated this by using slatteddoors which do not restrict airflow.

WATERLINES VOL.ll NO.1 JULY 1992 13

The questionnaire also revealed that100 per cent of the people use waterfor anal cleaning. So why not buildpour-flush latrines? In the circum-stances, it would seem to be anappropriate choice. WaterAid, in con-junction with the local population,constructed a gravity-fed water supplywhich provides water in sufficientquantities for flushing. (The watersystems are designed for a per capitaconsumption of 45 litres per day for a25-year design life, assuming a popula-tion growth rate of 2.5 per cent perannum and 40 per cent wastage).

A pour flush latrine would have anumber of advantages:o The siting problems would be greatly

alleviated as the latrines could beclose to the houses. It is thoughtthat if latrines are sited near dwell-ings they are more likely to be used.

o A pour-flush latrine is more effec-tive in controlling flies and odours.Because it has a waterseal and

providing there is an effective sealbetween the pit and the cover slab,flies and odours cannot escape fromthe pit. Latrines can therefore belocated near cooking areas.

o VIP latrines have no mechanism tocontrol mosquitoes. Mosquitoes arenot attracted to the light from thevent-pipe, but escape through thesquathole and into the environment.With pour-flush latrines there is noaccess from the pit. There is no needfor a dark latrine interior. If peoplefeel uncomfortable about using alatrine, not only are they likely touse it less frequently, but they willalso be less willing to keep it in ahygienic condition.

o People gave many reasons for want-ing to have a door. The addition ofa door is irrelevant to the function-ing of a pour-flush latrine, and onecould be built to any design.

o The cost of a pour-flush latrine needbe no greater than the cost of a VIP.

The questionnaires also revealedthat most children under the age of 10are not permitted to use the latrinesbecause their parents fear that childrenmight fall through the squathole and/ormess the cover slab. It is anticipatedthat by providing pour-flush latrinesparent's anxieties will be eased, andwith a greater emphasis allocated bythe health education team to promotechild usage, children from the age ofthree will use the latrines.

WaterAid is currently introducingpour-flush latrines on an experimentalbasis.

ReadingMacGarry, B., 'Development of the Blair VIP

latrine', Waterlines Va!. I No.4.Morgan, P., Rural Water Supply and Saniwtirlll:

Blair Research Blllletills, Macmillan, Lon-don, 1988.

Ryan. B.A. and Mara D.O., 'Ventilated im-proved pit latrines: Vent-pipe design guide-lines', TAG Technical Note No.6

15-22 August 1992. International Seminar on Ground-water and the Environment In Arid and Semi-AridAreas, Baldaihe, China. Contact: A. Skinner, IAH,National Rivers Authority, 500 Streetsbrook Road,Solihull, W. Midlands, 891 1QT, UK. Fax: +44 21 7112794.

30 August-4 September 1992. 18th WEDC Conferenceon Water, Environment and Management, Kath-mandu, Nepal. Papers will be presented by those withrelevant experience of work in developing countries.Topics include: rural water supply, low-cost sanitationand urban services. For information write to: MrsRowena Steele, WEDC, Loughborough University ofTechnology, Leies LE11 3TU, UK. Fax:+44 509211079.

31 August-3 September 1992. First InternationalConference on the Safety of Water Disinfection,Washington DC, USA. For more information, contact:Ms Diane Dalisera, ILSI, 1126 Sixteenth Street, N.W.Washington DC 20036, USA. Fax: + 1202 659 3859.1-4 September 1992. Aqua Tech '92, Amsterdam, TheNetherlands. The main theme of this year's event is '25Years of Water Technology as a Basis for the Future'.A two-day conference 'Recently identified pollutants inwater resources' will focus on the treatment of surfacewaters. filtered matter and ground water. More informa-lion from: Anita Kanters, RAI Press Department,Europaplein, NL·1078 GZ Amsterdam. The Nether-lands. Fax: +31 206464469.

28 September-1 October 1992. International Seminaron Supplementary Irrigation and Drought Manage-ment, Barl, Italy. Contact: Dr Atef Hamdy, IsitutoAgronomico Mediterraneo, via Caglia 23, Cap 70010,Valenzano (Bari) , Italy.

6-8 October 1992. Fifth International Pump Congress,

14

Karlsruhe, Germany. More information from: J. Huggel-meier, VDMA, 0-6000 Frankfurt/M. 71, Postfach 71 0864, Lyoner Strasse 18, Germany. Fax: +49 69 66 03511.

25-9 October 1992. Water Malaysia '92, Kuala Lum-pur, Malaysia. The 8th Regional Conference andExhibition of the Asia-Pacific Group (ASPAC) of theInternational Water Supply Association (IWSA). Theconference programme will cover source development,water-quality control and monitoring, water treatment,distribution and management. More information from:The Secretary, Organizing Committee Water Malaysia'92, c/o Office of Director of Water Supplies, PublicWorks Department, Jalan Sultan Salahuddin, 50582Kuala Lumpur, Malaysia. Fax: +60 3 2931557.

1-5 November 1992. International Conference onWater-Related National Disasters and their Environ-mental Impacts, Bangkok, Thailand. Contact: Prof.A. Das Gupta, AIT, GPO Box 2754, Bangkok 10501.Thailand.

10-12 November 1992. International Water and Efflu-ent Treatment Exhibition '92, Birmingham, UK.Annual show for the water industry; attracted 9000visitors in 1991. Details from: Paul Tweedale. ExhibitionSales Manager. Turret Group pic. Turret House, 171High Street. Rickmansworth, Herts WD3 1SN, UK. Fax:+44 923 771297.

1-5 December 1992. WATERTECH Indonesia,Jakarta, Indonesia. Being held as part of the 2ndInternational Exhibition and Conference on Equipmentand Systems for Pollution Control and EnvironmentalImprovement. Details from: Matthew Meredith, Over-seas Exhibition Services Ltd., 11 Manchester Square,London W1M 5AB, UK. Fax: +44 71 486 8773.

30 August-12 September 1993. 15th InternationalCongress on Irrigation and Drainage, Contact: Secre-tary-General. International Commission on Irrigation andDrainage. 48 Nyaya Marg, Chanakyapuri, New Delhi110021, India.

WATERLINES VOL.l1 NO.1 JULY 1992