Editing Water wheel (section)

=== Undershot wheel ===
[[File:Undershot waterwheel simple.svg|thumb|150px|Undershot waterwheel showing headrace, tailrace, and water]]

An undershot wheel is a vertically mounted water wheel with a horizontal axle that is rotated by the water from a low weir striking the wheel in the bottom quarter. Most of the energy gain is from the movement of the water and comparatively little from the head. They are similar in operation and design to stream wheels.

The term undershot is sometimes used with related but different meanings:
* all wheels where the water passes under the wheel<ref>{{cite web
|url=https://www.collinsdictionary.com/dictionary/english/undershot
|author=Collins English Dictionary
|access-date=12 February 2017
|title=undershot
}}</ref>
* wheels where the water enters in the bottom quarter.
* wheels where paddles are placed into the flow of a stream. See the stream above.<ref>{{cite web
|url=https://www.merriam-webster.com/dictionary/undershot%20wheel
|author=Merriam Webster
|title=stream wheel
}}</ref><ref name="PITLtypes">{{cite web
|url=http://www.powerinthelandscape.co.uk/water/water_wheels.html
|author=Power in the landscape
|access-date=12 February 2017
|title=Types of water wheels
}}</ref>

This is the oldest type of vertical water wheel.