Hydraulic ram pumps and Sling Pumps

Human Powered Water Lifting DevicesIntermediate Technology Development Groupenough to raise water from a maximum depth of about 7 metres.It should also be noted that if a shallow-well is used too much, the water-table may fall as theunderground reservoir of water is reduced. If this level falls below 7 metres, the pump will notwork.Four types of shallow-well pumps are shown below: rower, piston, diaphragm and semi-rotary.RowerThe rower pump is a simpler andcheaper version of the traditionalpiston pump (see below). Itssimple design means it can beeasily manufactured andmaintained using locally availableskills and materials. This type ofpump may require "priming",which means pouring water intothe cylinder so that the sealaround the piston is airtight. It isvery important that clean water isused, to avoid contamination ofthe pump and the spread ofwater-borne diseases.PistonPiston pumps, based on the same design asshown in Figure 1, are more widely used. Thereis a similar risk of contamination from dirtypriming water. In cases where the water is to bedelivered under pressure (such as to a villagewater mains) or to a point higher than thecylinder (such as a water storage tank), a "force"pump is required. The operation is the same, butthe design is slightly altered so that the top isairtight. This is done by putting a valve on thespout and adding a "trap tube" and air chamberwhich maintains the pressure (and therefore theflow) during the up-stroke.Figure 2:Rower pumpFigure 3: Shallow-well piston pumpDiaphragmThis design is often used for fuel pumps incars. The Vergnet pump is an adaptationof this principle for deep-well use, whichcan be used in crooked wells, where a rodoperatedpump would have problems, andwhich is fairly easy to maintain.Figure 4:Diaphragm pump2