The tub wheel in its simplest form is just a small undershot wheel mounted horizontally on a vertical axle. This configuration was developed in the early middle ages and was called a Norse wheel. Turned by the impact of a stream of falling water striking its paddles, its efficiency was increased somewhat by building a bottomless wooden tub around it. This tub harnessed more of the potential energy of the water before the water fell below the wheel.

The tub wheel is easy to build and maintain, and is fairly dependable. While it is not very efficient and does not generate a great deal of power, its relatively small diameter (usually less than six feet) allows it to operate at moderately high speeds, often eliminating the need for gearing. Sometimes it could be directly connected to the machinery it was to run. Small neighborhood mills often made use of tub wheels in the 18th and 19th centuries.