This is what borehole / water experts, governments and NGO's don't know.

Hundreds of millions of dollars have been spent hand drilling millions of boreholes in different locations around the world. Nearly all those boreholes were installed using methods "recommended" by people that are unaware of the most efficient and lowest cost method of drilling boreholes by hand, air lift reverse flow. As a result, we have a world where 30 percent or more of all the boreholes placed in Africa and other parts of the world have failed prematurely. https://www.unicef.org/wash/files/Guidance_Note_005.pdf

Governments and organizations need to be aware that they are paying for substandard boreholes installed by processes recommended by persons without full knowledge of all methods of borehole installation. As a result, hundreds of millions of dollars of government and private money have been wasted and will continue to be wasted.

The current 30% water point failure rate is an amazing mistake and something that should have never been allowed to happen or continue to happen, yet it continues today. https://www.unicef.org/wash/3942_59785.html

Today, boreholes are being installed using the same methods and tools. It is a sign of insanity for persons to continue to drill boreholes using the same methods and tools that have led to a 30 percent failure rate. As one looks through the UNICEF and other manuals available on the internet, one finds that there is a complete lack of understanding of reverse flow air lift drilling. And there is really no excuse for such a lack of knowledge. Air lift reverse flow drilling has been in use throughout the world for many years.

It is impossible to engage in an entire investigation, like the one in the first link, of the causes of borehole failure when one does not have a complete knowledge of the tools and processes used in the drilling industry. It is clear that UNICEF and other organizations are not informed about and do not know the benefits of air lift reverse flow drilling. When one does not know the costs and benefits of one method over another or the causes of failure inherent in one method of construction vs another, then one cannot reach a full understanding of the causes of failure of boreholes throughout he world. The conclusions reached by such a study, are by implication, incorrect. That is why this problem will continue to plague the borehole industry as it has after all other treatises of a similar vein.

For example, one should know that in "jetting", a type of direct circulation drilling, one can expect for there to be injection of thixotropic clays into an aquifer if one uses drilling mud or drills through thixotropic clay bearing formations. One should be aware that thixotropic fluids “set” after a period of time within a borehole. One should seek out drilling methods, like reverse flow, that do not force thixotropic fluids under high pressure into aquifers. However, there seems to be no warning in instruction manuals of the processes that cause problems due to clay injection in aquifers. And the lack of that knowledge can be the cause of a misunderstanding of the determining factor in the failure of water points.