Hand-dug or drilled wells must be adequately protected in order to provide water of sustaining quality. Wells should normally be sealed to a depth of 3 meters to prevent the entrance of surface water or low quality ground water. The top slab of the structure should be above flood level and all openings properly sealed to prevent contamination.
Often sanitary well seals are difficult to obtain in developing countries. Well seals are necessary to protect the water quality and to protect pumps from physical damage.