Sludging

Sludging is a very simple well drilling method developed in ancient India but still used extensively in developing countries, where capital is scarce, but manpower abundant.

A pipe is moved up and down in a hole filled with water (mud). Every time the pipe hits the bottom, some soil material is loosened and suspended into the drilling mud, which is continuously pumped out of the borehole by a valve, taking advantage of the same reciprocating movement.