The borehole stays open by water pressure. Thickeners such as clay, bentonite or even cow dung are usually added to the water in order to prevent hole collapse and reduce loss of working water (drill fluid).
===Suitable conditions ===
Suitable for unconsolidated formations: Sand, silt and clay. If rotated (including a drill bit) it may be possible to penetrate softer-consolidated formations such as stiff clays, soft sandstone, and weathered laterite.
===Construction, operations and maintenance===
Equipment is very cheap and can be produced locally.
==Costs== ==Field experiences===
Mainly used in India, Bangladesh, Nepal and Chad.
===Manuals, videos, and links===
* [http://www.practicafoundation.nl/wp-content/uploads/PDF/Practica%20drilling%20Rs%20versie%201th%20september%2005.pdf Rota-sludge and Stone Hammer drilling, part one: Drilling Manual] by Practica Foundation. [http://www.practicafoundation.nl/wp-content/uploads/PDF/practica-production-rs-versie-1th-september-051.pdf Rota-sludge and Stone Hammer drilling, part two: Production Manual] by Practica Foundation.
* Multi-service procedures for well-drilling operations, field manual chapter 9, US Military Chapter 9, alternative well construction, manual drilling techniques - [http://www.paulsawyers.com/pdfs/FM_5_484.pdf Download].
=== Acknowledgements===
* The basis for the material on this page was obtained from a desk study shortly to be published on the website of the [http://www.practicafoundation.nl/ Practica Foundation], and from the [http://www.rural-water-supply.net/ Rural Water Supply Network], and specifically its [http://www.rural-water-supply.net/en/implementation/manual-drilling manual drilling section].
* [http://www.lboro.ac.uk/well/resources/technical-briefs/43-simple-drilling-methods.pdf 43. Simple drilling methods.] WEDC.