Changes

Jetting is practiced in a wide range of varieties. The most simple consists of driving a plastic pipe down with water pressure from a motor pump (no drill bit and no rotation, with the water flow jetting the sand up). The depth is limited (no drill bit and extendable pipes). Other systems make use of extendable plastic or galvanized pipes and a drill bit and are rotated during drilling. With these systems greater depth can be reached.

Suitable for weakly cohesive sands and silts. Manual jetting is generally used up to depths of 35 meters.

==Construction, operations and maintenance==

All drilling equipment, except the motor pump and some valves, is locally produced.