installed in recent years consist of asteel pump stand bolted to the upperend of a steel borehole casing. Theoriginal Murgatroyd pump was set intoa concrete base, and some later modelsalso had this feature. The lateststandard models arc designed to bolton to a 150mm-diameter steelborehole casing, which makes totalreplacement of the pump head easy.Where the pump is fitted to a well, alength of borehole casing is cast intothe concrete weB cover. The use of16mm V-boILs which clamp the pumpto the casing, introduced by CecilAnderson, is a very successfultcchnique.

The wooden block, usually made ofteak, is cut, drilled and then boiled inoil for two or three hours, then allowedto cool overnight. This treatmentexpels air from the timber, and oil issucked in during the cooling phase.This treatment provides the block withself-lubricating properties, which areideal in situations where regular pumpmaintenance cannot be guaranteed.Mopane hardwood blocks are nowbeing introduced, as an alternative toteak, as the natural reserves of teak arebeing reduced.

The wooden block rotates around asteel bolt which is supported by steelbrackets welded to the upper end ofthe pump stand. In older designs thewooden block rotated around a lengthof 25mm steel pipe (pivot tube) whichwas clamped within a V-shapedbracket and held by a nut and bolt. Inthe latest standard pump, this is a35mm-diameter solid bright mild steelbolt equipped with a squared head toavoid rotation. The bolt is kept tightwith a single nut held against a spring

method of boIling the pump standdirectly to the borehole casing andcalled it the 'Bush Pump', Thisbecame the national standardhandpump, and most Bush Pumps inexistence today are of this type.

The period after 1980 saw aproliferation of Bush Pump models,many being inferior in design to theoriginal. As a result the governmentdecided to introduce new standards in1987. The 'Model B' Bush Pump,designed by government staff as aresult of a national co-ordinatedinitiative, is the current standard.

DescriptionThe hardwood block, which operatesas a bearing-and-Iever system iswithout a doubt the key feature of allBush Pumps. It was Murgatroyd whointroduced this piece of genius. Theteak or mopane block is robust,durable, and self-lubricating and stilloperates when old and badly worn. Ithas a life expectancy of at least onedecade and usually two. Such featureshave enabled this pump to outlast andoutperform most or its rivals.

Pump Head Most Bush Pumps

Dr Peter Morgan. Blair Research Laboratory,Ministry of Health, PO Box 8105, Causeway,Harare, Zimbabwe. Many Bush Pumps are found in very remote piaces.

The Zimbabwe Bush Pumpby Dr Peter MorganDeveloped under actual field conditionsto be almost indestructible, Zimbabwe'sBush Pump has been in service since1933, with modifications andimprovements. It is easy to build,requires almost no maintenance and isideally suited to local conditions.WHILE IT IS almost unknowninternationally, Zimbabwe's BushPump can boast of over half a centuryof successful operation in conditionsthat would have placed many othermodels on the scrap heap. When firstseen most Bush Pumps give theimpression of being a crude assemblyof metal parts - ideally suited for amuseum of past relics. The facts showhowever that this remarkable pump isa masterpiece of endurance, and canably perform when its parts are badlyworn out or even missing alLogether.

The Bush Pump is whollyZimbabwean. It was first designed, in1933, by Tommy Murgatroyd, agovernment Water Supply Officeroperating in the Plumtree District ofMatabcleland, in western Zimbabwe.Its success can be judged by the factthat no other pump, save the bucketand windlass, is more common in therural areas of Zimbabwe. It hasremained the pump of choice for alIheavy duty and alI deep well andborehole settings throughout thecountry ever since.

History of developmentFollowing its birth, the design of the'Murgatroyd Pump' remained almostunchanged for about 40 years, andmany of these early models, datingback to the mid-1930s are stilloperating today. The original pumphad been designed in a blacksmithingera, when standard pipe and plate werebolted together. The first major designchange took place in the mid-1970swhen Cecil Anderson, an engineerworking with the Ministry of Water,redesigned it, replacing the boltedstructure with components that werewelded together. He used a successful

24 WATERLINES VOL.8 NO.2 OCTOBER 1989

washer. Earlier head bolt systemswhich were fined wiLh a lock nut (andnot a spring washer) had a tendency tocome loose. The handle of all BushPumps is made from standard steelwater piping auached to the woodenblock with U-bolts.

The same arrangement of nut-and-bolt system is used to support thelinkage between the block and pumprod at the front end of the pump head.On the current standard the link ismade directly through a V-bracket.

The latest Model B Bush Pump,retains all the best features of earliermodels and these include thehardwood block, steel pump stand, U-bolt clamping system and solid pin-head bolts. This model has fewwearing parts, and unlike itspredecessors, has a direct link betweenthe rod and the block.

In this model the rod passesthrough a 'floating washer' systemwhich is able to accommodate allmovement of the rod, both forwardand back and from side to side. Twowashers arc used, the upper to supportthe rod (through a rubber buffer), thelower to form a hygienic seal. Themain wearing parts in the head arcreduced to the washers themselves,and the wooden block, Lhewear on thelauer being minimal. The washers are100mm-diameter discs of 6mm steelplate which should ideally be replacedevery two years, although the pumpwill operate effectively even if theseparts arc excessively worn. Two sparewashers arc provided wiLh each pumptogether with two spanners.

The Model B Bush Pump has beendesigned to operate (albeit lesseffectively) when most of its boltshave been removed, while oLher partscan be substituted with wire, steel pipeor non-standard parts. These featuresbecome all-important in Lhercal worldwhere pumps are just expected to workwith minimal assistance from outside.

Down-the-holecomponentsThe Bush Pump operates on a liftpump principle. The reciprocatingaction is transferred from the pumphead to the cylinder through a series ofgalvanized steel pump rods runninginside a steel rising main. Most risingmains arc made from 50mm GI pipingalthough 40mm is also used and even25mm on occasions. Most rods aremade of 16mm mild steel although12mm is also used. Standard 3mlengths of pipe and rod arc joined wiLhthreaded sockets or connectors. Pumpcylinders are made of brass and are

The Model B Bush Pump.either 50mm or 75mm in diameter,most being 75mm, these are locallymanufactured. The pistons and foot-valves are also made of brass withmost piston seals being made oflcaLher. Standard foot-valves arc veryrugged and reliable, when the rightmodel is chosen. Galvanized pipes androds have been found to be durable inmost Zimbabwean waters, and whilecorrosion problems do occur, Lhey aremuch less intense than elsewhere inAfrica.

CharacteristicsBush Pumps are installed in communalseuings throughout Zimbabwe wherethey may serve several hundredpeople. In many cases they areexpected to work for over 15 hours aday.

Bush Pumps can lift water from adepth of 100m, but most are installedto depths of about 40m. The pump isvery flexible, however, and will alsooperate effectively on shallow wells.Most pumps arc fitted with standard75mm brass cylinders which enablethem to deliver between 30 to 40l/min. This discharge rate is reduced atgreater depths and also when theleaLher seals are worn or the foot-valveleaks. 50mm cylinders deliver between15 and 20 l/min. The stroke length isvery variable, but normally lies

between 100mm and 200mm. Thedownstroke is cushioned by a rubberbuffer. The upstroke is stopped whenthe steel handle hilS the ground.

Several parts of the Bush Pump arcsubject to wear, especially in someolder models. In the latest model,wearing components in the head arereduced to a minimum, as describedearlier. In all cases the rate of wear ofthe underground parts depends on Lheamount of use the pump received andthe quality of the water being pumped.Water containing sand or sedimentleads to greater wear of the seals,which may need replacement everyone or two years. Seals which are75mm wear less rapidly than 50mmseals since they travel smallerdistances for every litre of waterpumped.

Steel rising mains and rods alsobreak, wear and corrode for variousreasons. Rod separation may resultfrom unscrewing sockets or the rodssnapping at the the threaded joint.Sixteen millimetre rods are preferredsince they are about three times asstrong as 12mm rods. Since both rodsand rising main are taken apart eachtime the piston seals are replaced, thethreading of the joints is also subjectto wear or damage. For this reasonmore attention is being paid to fullyextractable valve systems, where sealreplacement can be done without

WATERLINES VOL.8 NO.2 OCTOBER 1989 25

Table 1. Frequency analysis of breakdowns and repairs carried outby DDF handpump maintenance teams on Bush Pumps 1987-8

Note: Data from DDF. Many of the parts of the old standard Bush Pump have beendispensed with in the later Model B Bush Pump. This move took note of the old saying, 'Thedesigner knows he has reached perfection, not when there is no longer anything to add, butwhen there is no longer anything to take away'.

B. Pump head (old standard model)

Part No. Repairs

A. Down-the-hole componentsPart No. repairs

pumps. However confidence in steelcomponents below ground remainshigh, because alternatives that operatewell at the required depths are notavailable, and there is much expertisein handling of steel fittings which areavailable.

Some pumps break down simplybecause the down-the-holecomponents fall apart - a symptom ofpoor assembly by less-experiencedpump maintenance staff. In recentyears, however, pump minders andpump fitters have undergone far moretraining and have more educationalliterature available to them. It is hopedthis will reduce the number of visitsmade to pumps that literally fall apart

Village-level maintenanceVillagers and pump caretakers have animportant role to play in themaintenance of the Bush Pump byensuring that the nuts and bolts on thepump head are tight. Modern pumpsare sold together with simple tools,which can be used on the pump head.The spanners are usually left with thepump caretaker or chairman of thevillage water committee. Villagers arealso responsible for keeping thehead works (apron and water run-offarea) clean.

Village maintenance of down-the-hole components is not easy with theBush Pump, however, and is rarelypractised. This is partly becausepumps have always been consideredgovernment property, and partlybecause the pipes are heavy to lift,especially from the deeper boreholes,where special equipment is required.When the pumps are sited on remoteboreholes where no alternative sourcesof water are available, however,villagers. actively support themaintenance teams. Lifting equipmentin the form of mopane poles filledpermanently in place above the pump.The mopane poles are common indrier parts of the country, and thisreduces the amount of equipmentwhich must be moved to service thepump. Community participation inmaintenance is less common in areaswhere alternative sources of water areclose to the surface and where river orwell water may be freely available.

Bush Pump researchThe relatively high cost of maintainingBush Pumps is mainly due to highcosts of conveying trained staff andequipment to the remote sites wherepumps are oftcn located. While thcpump head can be adcquately serviced

64333322218

231311862

63%

37%

100%

%Total

% Total

service and maintain the handpumps.Currently the number of Bush

Pumps operating in Zimbabwe isestimated at about 16,000, the cost ofmaintaining these pumps (1987/88DDF figures) being around Z$1.3million per annum (1987/88 DDFfigures show that 8,391 Bush Pumpswere serviced at a cost ofZ$I,296,067). On average each pumpcosts around ZS 150 to maintain everytwo years. These high figures reflectthe simple fact that each Bush Pumpmust be serviced by well-equippedgangs, who travel great distances toreach the pumps. Under suchconditions most gangs respond only tobreakdowns. The more recentintroduction of trained pump mindersoperating at ward level is intended toreduce the costs of maintenance. DDFfigures show that 89 per cent of BushPumps are operational at anyone time,alLhough there is some variation fromdistrict to district.

Most visits arc made to BushPumps to replace the piston seals,which have an average life span ofaround two years. Failures of therising main and rods are notuncommon, especially in ageing

587350296279278262227216204146814

2,2911,3131,065748600232

LeathersPipesRodsFoot-valveCylinderOther

Subtotal

M24 boltsTee pieceM12 boltsGuide pipeLink armBase plateM16 BoltsSleeve pipeBlockStandOther

Subtotal

Overall total

disturbing the rising main.Bush Pumps are manufactured by

several engineering companies inZimbabwe. A mass-production linecapable of manufacturing 200 ModelB Bush Pumps per month has beenestablished at V and W Engineeringand Installations in Harare.

MaintenanceAs with all handpumps, the success ofthe Bush Pump in providing a reliablewater supply depends upon aneffective maintenance and repairsystem. In Zimbabwe maintenance ofthe Bush Pump has for many yearsbeen the responsibility of the DistrictDevelopment Fund, a departmentwithin the Ministry of LocalGovernment, Rural and UrbanDevelopment. The DDF operates atdistrict level and employs pump-fiuinggangs under the direction of theDistrict Field Officer (Water). Thepump-fiuing gangs are equipped withspecial tools to maintain Bush Pumpsand other water installations. Morerecently pump minders equipped withtools, and travelling by bicycle havebeen employed at Ward level to

26 WATERLINES VOL.8 NO.2 OCTOBER 1989

by keeping boILs tight, a task whichcan be performed by the local pumpcommillee, repairs and maintenance ofdown-the-hole components is not soeasy.

Since 1985 government staff havebeen actively involved with a researchprogramme aimed at simplifying BushPump maintenance, especially of thedown-the-hole components. This is anongoing programme, which takes timeto fulfil since faulty concepts andinadequate design in handpumps oftentake years to reveal themselves.Three main avenues have been triedto date, these are:

o 50mm extractable brass footand piston valve with 50mm GIrising main;

o 65mm extractable piston valvewith 65mm GI rising main;

o 40mm and 50mm polyethylenerising main with 50mm and75mm cylinders;

The more recent tests are beingcarried out on the Model B head,which can be adapted to suit a numberof rising main and rod types.

The extractable piston and foot-valve system was developed by V andW Engineering in 1986. In this systemboth the piston and foot-valve can beextracted through a standard 50mmsteel rising main with the pump rods.Both 12mm and 16mm mild steelpump rods can be used, and these arethreaded together. A female acmethread has been introduced into thelower inner surface of the piston valveand a matching male thread fitted tothe upper end of the foot-valve. Thefoot-valve press fits into the base ofthe cylinder. The piston seals are madeof neoprene. The piston valve can beextracted directly by hand through therising main. The foot-valve is lifted byscrewing the piston valve down on tothe foot-valve and using the leverageof the pump to extract it.

Another system uses extractable65mm piston valves. This wasdeveloped by government staff toimprove the water discharge rate andretain extractability. In this design a65mm-nominal-bore brass cylinder isexpanded and threaded above to fit a65mm GI pipe, reduced in diameterand threaded below to fit a 50mmheavy-duty brass foot-valve. Thepiston is fully extractable, has largerparts and the seals wear out moreslowly compared to the 50mmextractable type. In those pumps beingused in trials standard 16mm mild

steel rods are used.In this system the chosen foot-

valve is a well-proven reliable designthat IS known to provide several yearsof service before attention is required.The delivery rate of this system isintermediate between the 50mm and75mm cylinders and is about 30 Vmin.

The 65mm GI pipe used in thissystem costs about 25 per cent morethan 50mm pipe, and is heavier.Obviously specialized equipment isrequired to raise and lower risingmains of this typc, but with the chosenfoot-valve in place, lifting takes placevery rarely and is· part of themaintenancc system that could beundertaken by districtteams. The greatadvantage is that piston sealreplacement, which is the mostfrequent service requirement, can beundertaken quickly and easily, bypump minders, which results in muchreduced maintenance costs.

Model B Bush Pumps are alsobeing tried with heavy-dutypolyethylene rising mains equippedwith flexible 12mm EN8 steel/steelrods. 40mm and 50mm pipes havebeen chosen for tests so far, filled with50mm and 75mm brass cylindersrespectively.

When the piston/cylinder/foot-valve assembly requires inspection,the whole rising main/rod system ispulled out at one time. So far thissystem has been tried satisfactorily toan 18mdepth.

Traditionally leather seals are usedin Zimbabwe, but neoprene seals arealso being examined in combinationwith brass cylinders, and nitrile rubberseals are being examined incombination with stainless steelcylinders. Clearly there is anadvantage in extending the workinglife of seals, as the frequency of visitsand related costs will be reduced.

Requirements forprogramme successIf Zimbabwe's handpump programmeis to succeed, some 40,000 BushPumps will be required together withan effective maintenance system toback them up. As the number ofpumps increases, so does the pressureon staff and resources of the DDF whomaintain them. Consequently itbecomes increasingly essential thatmaintenance procedures should besimplified so that the users themselvescan playa much more active role inmaintenance, especially of the down-the-hole components.

While time-tested conventionaldown-the-hole components continue to

The early Murgatroyd pump.

be used, an ever-increasing number ofpumps are fitted with easier tomaintain systems. Only when thesenew systems are thoroughly tested andproven, will they begin to takeprecedence over more conventionalpractice. Great care and constraint isrequired however before dramaticchange takes place, especially fordeeper settings where alternativevalves. rods and rising mains may fail.

Zimbabwe is fortunate in havingchosen the handpump option long agoso there is much experience to drawon. Today this long experience iscautiously being combined withtechniques of a more recent age. TheBush Pump is so firmly established inZimbabwe, that it is unlikely to bereplaced by any other model for theforseeable future. As past historyshows, Bush Pumps last for far toolong for that to happen.

AcknowledgementsI wish to thank Ephraim Chimbunde,Fambi Gono, Joshua Mazanza,Philimon Ngororo and their supportingstaff for their assistance in fieldoperations. I also wish to thank RolandHaebeler, Jim Holland, Marcus Sharp,Peter De Villez, Erwin von Elling,Walter Wall Bake and David Williamsfor their advice, support andencouragement. I am also indebted toMr Mudege and his staff with theDDF for their support and assistancein Bush Pump research anddevelopment. I thank the PermanentSecretary for Health for permission topublish this article. ~

WATERLINESVOL.8 NO.2 OCTOBER 1989 27