Hydraulic ram pumps and Sling Pumps

you enlarge the hole, more water will flow out. Therefore you should make all preparations inadvance, having all tools and material at hand. The best way to do the job is with two people. Oneprepares the hole for sealing, the other prepares the material. As you have experienced during thetest, there is a very short time span during which the cement is still plastic. This is the right timewhen the cement has to be forced into the hole. Experience has shown that the best tools for thisjob are a screwdriver used as a chisel, a light hammer, and a piece of timber a little bit smaller thanthe hole. With the chisel shape the hole like a swallow-tail, if possible, pressing the cement into thehole at the right moment using your thumb. Take the timber piece and the hammer at the lastmoment before the cement sets and press the plug in by hammering the timber. This trick is likely towork if the leak is not big and some tests are first made to find out the cement's exact setting time.A:ll that is required for this repair work is fast action.Sodium silicateThis is a water-clear viscous liquid. It can be tried to seal leaks if the water flows out withoutpressure. Prepare the base for the job using sandpaper to achieve a slightly rough surface of thecement wall. Open the bottle or container with sodium silicate only when you have completedpreparations, since this chemical hardens on contact with the air. Use a spatula or a thin metalsheet to apply it, using the same technique as described for the nil coat. The sodium silicate shouldcover an area slightly larger than the leak. This method has often been used with much success.Even if the two methods for sealing the tank from the outside remain unsuccessful, they have notdone any harm to the structure and do not influence the professional repair work required forferro-cement structures, since the rapid setting cement or the sodium silicate can be chipped offtogether with the-original cement mortar.The repair work requires the same attention to the quality of material and mixing as the constructionwork. If the sand which was used for construction is not available, or if the source of sand isunknown since the repair work only becomes necessary years later, material must be tested inaccordance with Chapter 3. It is again important to sift the sand through gauze wire mesh (mosquitowire mesh). Mixture should be three parts sand with one part cement. There is a considerable risk ofcreating a new leak since different mixtures result in different expansion of this material. This mightlead to the patch cracking away and leaking at the edges. It has therefore also to be stressed thatthe original construction work should follow strictly the advice given. It can sometimes be observedthat the amount of cement is increased to be on the safe side. This is unnecessary and can result inrepair problems since after some years there will be nobody who remembers the original mixture.Repair of ferro-cement tanks should not be done using other than normal Portland cement. We canonly warn against the use of e.g. rapid setting cement, since the property of this material differsgreatly from the original Portland cement, as shown in the example above. Different expansion alsocreates problems likely to result in new leaks if the mortar for repair is wet. Although the usuallysmall patches can be filled with mortar containing more water than the original material, this seal willnot last since the material will shrink and by doing so will most likely result in another leak. Smallleaks should be opened by using a chisel and hammer, chipping the mortar around the leak, downto the chicken wire. This must be done from inside the reservoir. It can happen that the leak insidethe tank is not visible at the wall. In this case hammer a nail through the wall from the outside. Thishas to be done rather carefully, knocking the nail with short hammer movements. Use a thin 2 1/2inch nail. Where the nail appears inside is not necessarily the point of leakage. In all those caseswhere this method has to be used, the surrounding area with a diameter of 150 mm should bechipped away. This job must be done carefully so that no cracks develop on the outside, since thispart of the wall will remain untouched. The nail should be pulled out again.Preparations to be made for the patch differ depending on whether the tank is in use, meaning wateris purposely drained, or there is a minumum of water left and/or the leak occurs in an upper part ofthe wall where the ferro-cement is rather dry. If the area of repair is dry' it is necessary to wet it by61