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Sludging is a manual drilling technique in which water is circulated to bring the cuttings to the surface. The drill pipes are moved up and down. On the down stroke, the impact of the drill bit loosens the soil and on the up stroke, the top of the pipe is closed by hand (or a valve), drawing up the water through the pipe and transporting the cuttings to the surface. On the next down stroke, the hand (or valve) opens the top of the pipe and the water squirts into a pit, in front of the well. In this pit, the cuttings separate from the water and settle out, while the water overflows from the pit back into the well.

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 ==

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Equipment is very cheap and can be produced locally.

Mainly used in India, Bangladesh, Nepal and Chad.

* [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.

* Self-help wells, R.G. Koegel, FAO 1985. Internet manual on hydrogeology, well constructions, all drilling techniques - [http://www.fao.org/docrep/X5567E/x5567e00.HTM website].

* Human-Powered Drilling Technologies, Richard Carter, Cranfield University, 2005 - An overview of human-powered drilling technologies - [http://www.rwsn.ch/documentation/skatdocumentation.2005-11-15.5533687184/file Download].

* 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].

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