Groundwater quality : an important factor for selecting handpumps

Handpumps are considered to be the most economical means for utilizing - grou.idwater for millions of people in rural and urban fringe areas in many developing countries. Large numbers of handpumps have already been installed and many more are planned to be put into operation during the coming years.

Based on the experience with the World Bank executed UNDP-INT/81/026 Handpumps Project, particularly in the West African Region, the groundwater quality can have a significant impact on the performance of handpumps, and thus, on investment and recurrent costs. This is especially the case where handpumps with non-corrosion resistant below ground components (rising mains, pump rods, cylinder assemblies) are applied under corrosive groundwater conditions resulting in an increase of the frequency of breakdowns. Field experience has shown that up to 2/3 of handpump breakdowns have been directly or indirectly attributable to corrosion (rod breakages).

Therefore, corrosion resistance is an important point with regard to handpump selection in order to minimize maintenance costs. Corrosion resistant material, e.g. stainless steel, however, is generally more expensive than noncorrosion resistant material like galvanized iron, which is still the standard material for many and widely applied handpumps such as the India Mark II and others.

As a consequence, it is essential not only to look at the price, when hand-- pumps are to be selected, but also at the long term maintenance costs, e.g. over 10 years or more. Therefore, in order to avoid any surprises, the groundwater quality should be taken into account so as to verify whether corrosion resistant handpumps, even at higher prices, would offer a more economical solution on a long term basis than the usually cheaper non-corrosion resistant handpumps.

However, corrosion has not only a direct economical impact on handpumps as referred to above, but also an indirect one due to corrosion products affecting the water quality. The result of this are high iron concentrations in the water causing reluctance from the part of the beneficiaries to use such water points for domestic purposes or even abandonment of them with the consequence that the financial, means allocated to such water points are badly invested. Field experience suggests that up to 30% of handpump equipped water points are very little or not used mainly due to corrosion related water quality problems.

Furthermore, it becomes more and more evident that the corrosion problem with handpumps is not only restricted to West Africa, where the experience presented in this paper comes from, but occurs all over the world. It is, thus, imperative to take 'the factor of corrosion into consideration in connection with selecting handpumps and, as a rule of thumb, galvanized iron or mild steel should not be considered as material [author abstract]