The cost of a manually drilled well can 10% to 50% of machine drilled or hand dug well to similar depth. Hand drilling equipment can often be readily taken to sites which larger, more conventional drilling cannot access. However, it is important to note that hand drilling techniques are extremely effective in appropriate ground conditions. They are not suitable beyond their hydrogeological limitations. In cases where the formation is too hard, or the water bearing formation too deep, conventional drilling is the preferred option.
Unlike hand digging, which requires a person to be physically below ground to dig the well (of at least one meter in diameter), hand drilling enables the operators to remain above the ground and drill a narrow diameter borehole (50 to 200mm). Hand drilling can provide highly affordable improved groundwater sources for households and communities for both domestic and productive use. Drilled depths depend on the technology and formation, but can extend to 30m and sometimes more.
The auger method involves penetrating the ground with a small-diameter borehole with a cylindrical or helical soil auger. This method can penetrate certain sands and silts and some clay formations.
Hand percussion and stonehammer drilling involve the lifting and dropping a cutting tool suspended at the end of a rope. They are dry techniques, only adding a little water in order to remove the spoil (drill cuttings).
In contrast to the above, the jetting and sludging methods use considerable amounts of water to wash out the spoil. Jetting (also known as washboring) and the EMAS technology inject water down and out the bottom of a drilling pipe to wash the spoil up to the surface. Self-jetted well-screens are an improvement of the original jetting technique. The use of a cutting point when jetting enables more compact materials to be drilled. A tripod (or derrick) enables the technique to penetrate deeper. The EMAS technique uses a percussion action coupled with back and forth rotation of the drill bit to break the formation, whereas jetting is designed to penetrate mainly sands and silts with the force of the jetted water.
Sludging and its more recent modifications (Baptist, Rota Sludge and Pounder Rig) are all continuous drilling methods that allow the drilling fluid to flow down the annulus (ie the gap between the drill pipe and the drilled hole) and carry the cuttings up through the drill pipe. The Baptist method, Pounder Rig and Rota sludge have all tried to penetrate harder formations, with varying success. The Pounder Rig places the more emphasis on drilling of a vertical hole, whereas the Baptist and Rota Sludge techniques emphasise very low cost wells. The Baptist and Rota Sludge techniques can be combined with stonehammer drilling to penetrate harder formations (eg laterite) whereas the Pounder rig is already designed for this.
For a comparison between different hand drilling methods and other drilling techniques see:
- Human Powered Drilling Technologies. An overview of human powered drilling technologies for shallow small diameter well construction, for domestic and agricultural water supply by R.C. Carter, Cranfield University at Silsoe, UK
Hand drilling techniques are extremely effective in appropriate ground conditions but are not suitable beyond their hydrogeological limitations.
These webpages are intended to enable more information exchange and discussion on hand drilling. They are by no means exhaustive. Please tell us more about your hand drilling experiences, projects that you know about or equipment suppliers.