Hydraulic ram pumps and Sling Pumps

-Choose the reservoir size according to the advice given in Chapter 2.4. Remember it is usuallycheaper to build one large reservoir than two smaller ones which add up to the same capacity.Figure 6.1 shows a 68-m3 reservoir built at Hill School, Lobatse, Botswana, where rainwater fromthree roofs is drained into one tank.-Mark the diameter of the tank foundation on the ground to make sure no passage is blocked by theproposed reservoir. Methods of bridging downpipes are explained in Chapter 7.-In Tables 8-14 (p. 88-91) the amount of material required is specified, including a calculation forwastage. Sand for mortar and the number of bricks required are based on a brick size of 110 mm x230 mm x 70 mm in Southern Africa. If your brick size differs considerably, you must recalculate thenumber of bricks and the amount of sand and cement required for bricklaying. Slight differencesshould be ignored. In Botswana, cement bricks have been used, but burned clay bricks can be usedif available according to standard. As tests for quality need to be made in a laboratory, finding outabout the quality of a brick on the work site is very difficult. If the supplier cannot submit a certificate,and there are doubts about the quality of the bricks, they should be sent for testing before they areused. For example, if a back is not as hard as it should be for brickwork, you can rub dust off it withyour hand. Bricks should be hard-burned and blue in colouring, rather than red in colouring. Burnedbricks often differ in size. This makes working with them more difficult and requires skilledbricklayers. If bricks differ in length, build up the wall from the inside to achieve a smooth surface, asthis is the side where the waterproof plastering must be done.- When the material is on site, and arrangements have been made for securing storage space, markthe external diameter of the foundation on the ground. Different techniques for unstable ground arediscussed in Chapter 5.2. In principle, these techniques are the same as those required for thereinforced bricktank. The foundation trench can be dug only after the topsoil inside the circle hasbeen removed. All measurements given in the technical drawings assume the ground is stable. Incases where topsoil is not of equal depth, it must be removed to the greatest depth required to hitstable ground at all points (e.g. if the topsoil is about 300 mm in depth, it must be dug out entirely, asthe foundation can only start at that depth). When all topsoil has been removed to stable ground,levelling can begin. If there is no topsoil, a foundation should be dug to 100 mm before the trench isdug. This is usually necessary to avoid soil erosion. If there are pockets of topsoil after a layer of100 mm has been removed, they must be filled with lean concrete. When all topsoil has beenremoved and the stable ground has been levelled, the ring foundation should be dug as shown inFigure 5.3.1. Measurements for the size of the ring foundation and the thickness of the slab are thesame for all tank sizes. All tanks with an internal diameter of 5.5 m or more require a centre pier tosupport the roof slab (for foundation see technical drawing).Reinforcement work must be done on site, but a metal workshop should probably bend the stirrups,as they must be of equal size and shape. Dimensions given for the rods are the minimum. It isalways possible to increase the dimensions if the scheduled size is not available. For the wallreinforcement, this is crucial. Vertical rods in the wall and ring reinforcement, which can be donewith 6-mm rods, should not exceed 10 mm in diameter. This is necessary, as rods cannot disturbthe brick bond or the joints which are equal in size. As Figure 6.4 shows, the reinforcement must beplaced in the centre of the wall. It is therefore imperative to fix the vertical rods precisely onto thefoundation reinforcement and to make sure they are not dislocated during the process of concretingthe foundation and ground slab. The horizontal ring reinforcement must be tied to the vertical barsfrom inside, using binding wire and pliers as shown in Figure 6.2. As the joints can be only 10 mmthick, and the reinforcement steel must be covered entirely by cement mortar, any dimensionexceeding the one indicated will cause problems. Reinforcement not covered with cement mortarwill rust. Therefore, flush-jointed bricklaying is necessary. To maintain the required height andassure an equal and. solidly filled brick wall, all courses should be indicated on a timber board whichshould be used as a control mechanism. As shown in Figure 6.5, keeping all vertical bars in positionwhile bricklaying is usually difficult if the height of the tank exceeds 2.00 m. For taller structures,rods can be cut into two pieces, extending the one fixed into the foundation in such a way that itoverlaps the other rod by at least 100 mm. The rods should be tied tightly together, above the65