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Water for the WorldWell constructed cisterns play animportant role in providing familieswith an accessible supply of potablewater. Cisterns and storage jarsconstructed of locally availablematerials offer improved access towater supply in many areas where goodsupplies are limited. They also pro-vide a means of controlling the waterquality.This technical note describesconstruction steps for building rein-forced concrete cisterns, ferrocementtanks, and medium and large reinforcedmortar storage jars. The stepsdiscussed are offered as guidelines andcan be changed to fit local needs andsituations. Before attempting theconstruction of any cistern, seekadvice and assistance from peopleexperienced in working in concrete andferrocement construction.

bseful Definitions \FERROCEMENT - An economical and simple-to-use type of reinforced concrete madeof wire mesh, sand, water and cement.VOIDS - Empty spaces; open areas be-tween narticles or substances.

Materials NeededBefore beginning the constructionprocess, be sure to have the followingitems:1. A plan of the cistern showing thedesign and dimensions as shown inFigure 1.2. A list of materials, tools andother supplies needed to complete thejob. Similar to the list in Table 1 or2. All materials should be availablebefore construction begins in order toavoid delays.

Table 1. Sample Materials List for aReinforced Concrete Cistern

Item

LaboF

Supplies

Table 2. Sample Materials Listfor a Ferrocement Cistern

Construction Steps for a ReinforcedConcrete Cistern

Follow the construction steps below.Refer to the appropriate diagramsduring the construction process.

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Drain and ,.ditch \ ILIba.

Ground surface

Length foundationlTOP Cover length .]

NOTE: Water may be pipeddirectly to dwelling

Figure 1. Plan for Household CisternL

1. Find the best location near the 2. Dig out a base in the ground tohouse to build the cistern. It should fit the dimensions of the cistern. Thebe located on high ground for good hole should be only 50-100mm deep.drainage and should not be located This will allow installation of ancloser than 15m to the nearest waste outlet near the bottom of the cisterndisposal site. Once the site is to take advantage of the entire volumelocated, mark it out using a measuring of the cistern. Level the excavatedtape, wooden stakes and cord, as shown area using flat-nosed shovels andin Figure 2. scrapers made from wood.2

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1Dwelling

Stake

Figure 2. Marking Cistern Site

3. Prepare the forms for the struc-ture. Use plywood sheets, ifavailable, for the faces and smallpieces of wood for bracing. All form-work for the cistern should becompleted before any concrete ispoured.l Nail all forms together to thedesign size of the cistern. Wallsshould be 200mm thick.l Brace the forms well. Place smallholes in the forms and slide wirethrough them. At the end of each pieceof wire, attach a stick to hold thewire in place. Then tighten the wireto create enough pressure to withstandthe force of the poured concrete. SeeFigure 3. Dirt should also be piled upagainst the outside of the walls togive them support against the weight ofthe concrete.

Inner form Wooden braces

,I

L shaped reinhrcing rod foundationto strengthen wall

,Figure 3. Forms for Cistern Walls

l Place reinforcing rods in theforms. For best results, lay the rodfor the floor in a grid pattern asshowninFigure 4. The cross barsshould be long enough to cross theentire length of width o f the floor andextend at least 300mm into the wall.The reinforcing rods should be bent tofit into the wall forms to a height of300mm. Other lengths of rod are thentied with these lengths to complete theinstallation of the reinforcing rod.This technique is recommended to pro-vide a solid connection between thewall and the floor. Figure 4demonstrates the placement of rein-forcing bars in concrete. The steelbars should be separated 150mm with thefirst cross bar laid 75mm from the edgeof the pour. The bars should be placedone third of the distance from the out-side or, as in the example given, about70mm in from the outside edge.

4. Make holes in the form for place-ment of the overflow and outlet pipes.The pipes should be placed directly inthe forms when pouring the concrete toensure a good pipe installation.5. Oil all forms before pouringconcrete. Use old motor oil or otheravailable lubricant to prevent theconcrete from sticking to the forms.6. Formwork and steel bar placementfor the cover follow the same pro-cedures as outlined above. After formsare complete, mix the cement, sand andgravel in a 1:2:3 ratio adding 23liters of water for each bag of cement.These proportions will ensure a thickpaste.Pour the floor and about 200mm upthe side of the wall in the first pour.Tamp down the cement with steel rodsand shovels to make sure that all voidsare filled. Once all reinforcing rods

are attached, finish the pour, tamp themixture well and smooth all surfaces.Cover the concrete with canvas,burlap, empty cement bags, plastic orother protective material to preventloss of moisture. Keep the coveringwet so the concrete does not become dryand crack. When pouring the cover, besure to leave an opening for access tothe cistern. The opening should befitted with a cover which either can belocked or is difficult to remove.

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Reinforcing L bar

Working concrete floor

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