Hydraulic ram pumps and Sling Pumps

After roof shuttering has been finished, the entire opening of the tank covered and gaps filled withpaper to ensure that concrete cannot pass through, the roof can be concreted. The concrete shouldunder no circumstances be wet and the mixture remains one part cement, two parts sand, one partballast.5.3.8 AlternativeThe roof structure described in Chapter 5.2 can also be used for this type of tank. But remember itrequires a centre pier and the double reinforcement of the centre of the tank floor. This means thedecision should be made before the construction work starts. It is also possible to use the roofstructure of the tank described under 5.1 but this requires welded reinforcement mesh orreinforcement rods as described in this chapter.5.4 Repair of ferro-cement reservoirsRepairing a ferro-cement tank is easy but should not encourage slipshod work. If the structure isfinished and cured as described, then no leaks are likely to occur. Small leaks which create only awet stain need not be attended to, since they will close after some time. Only leaks where waterflows out have to be repaired.The major problem is not the repair work as such, but the fact that leaks usually cannot be identifieduntil the reservoir is filled. As indicated earlier, the value of the water which is then wasted should beconsidered. As mentioned, curing after the structure is finished as well as while it is still underconstruction is just as important as the quality of craftsmanship and material. But, to make it entirelyclear, no reservoir -and this applies to the bricktank as well -should ever become entirely dry. Onlycement structures which never dry off remain waterproof in the long term. This means that, after thecuring period ends, a reservoir has to be flied with water. If as is the case in Botswana there arelong periods without rain, or even a drought, a reservoir cannot be kept without water until raineventually occurs. Thus it is advisable to fill the cistern with borehole water. This will not onlypreserve the structure, making curing unnecessary, but also furnish immediate evidence of anyleaks. If there is no rainfall some days after the structure is finished, and the necessary amount ofborehole water is not available, a minimum filling of 100 mm is a must. Since reservoirs might bebuilt in remote areas with almost no access to water and the likelihood of rainfall doubtful, theminimum fill must be provided. In addition, especially in hot arid climates, the structure must becovered on all sides with plastic foil in such a way that the moisture of the mortar cannot evaporate.This means the plastic sheets must be tied up with overlaps so that the wind cannot blow themaway. If a leak appears when the tank is eventually filled with rainwater, it is more appropriate toconsume the water than drain it to repair the leak. Two different methods of sealing an already filledreservoir from the outside can be tried, provided the material needed is available. However, there isno guarantee that these methods, or rather tricks, will seal the tank, but since they do not affectprofessional repair, they might be tried if large amounts of water are at risk.Rapid setting cementIf it is possible to obtain a few kgs of this cement, make a simple test before you buy it. Take a cleantin, pour in some clean water, and add some cement slowly, stirring it with a stick. When thewater/cement mixture becomes plastic, take some of it in your hand and mould it. This cement mustbecome very warm in your hand and by the time the heat disappears it must harden instantly. If thistest fails to produce the required result, you have either got the wrong cement or the material isoverdated, or has become moist, losing its property, and cannot be used. If the test is successful,buy the amount you estimate you will need. At the tank leak start to enlarge the hole where the wateris running out. The hole should at least be 10 mm large and just touching the reinforcement. While60