• 12 parts
  • Checked October 2026

Parts of a Water Wheel

A mill wheel in its setting: name the buckets, shrouds, arms, axle, flume and races, then three kinds of wheel.

Parts of a Water Wheel

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12
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Write the name of each numbered part.Answer key

  1. Buckets
  2. Axle
  3. Arms
  4. Shrouds
  5. Headrace
  6. Sluice gate
  7. Flume
  8. Tailrace
  9. Wheel pit
  10. Overshot wheel
  11. Breastshot wheel
  12. Undershot wheel

Own drawing from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the parts of a windmill

All 12 parts on the diagram

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The wheel 9

  1. Buckets They fill with water, and the weight turns the wheel.
  2. Axle The shaft the wheel turns on. It carries the power into the mill.
  3. Arms They join the rims to the axle, like spokes.
  4. Shrouds The two rims of the wheel, with the buckets between them.
  5. Headrace The channel that brings water from the mill pond.
  6. Sluice gate A gate that controls how much water reaches the wheel.
  7. Flume The last length of trough, carrying water onto the wheel.
  8. Tailrace The channel that carries the water away from the wheel.
  9. Wheel pit The pit that the lower part of the wheel hangs in.

Three kinds of wheel 3

  1. Overshot wheel The water arrives at the top of the wheel.
  2. Breastshot wheel The water meets the wheel about halfway up.
  3. Undershot wheel The water pushes the lowest part of the wheel.

How this list was compiled: Every name checked on 2026-10-01 and kept only where two of these use it. (1) Wikipedia, Water wheel, Watermill and Mill race, text only, https://en.wikipedia.org/wiki/Water_wheel , https://en.wikipedia.org/wiki/Watermill and https://en.wikipedia.org/wiki/Mill_race : the race feeding the wheel from the mill pond is the headrace and the one carrying it away is the tailrace; the final approach to the wheel is along a flume; sluice gates control the passage of water; buckets on the outer rim; rim or shroud; axle; wheel pit; overshot (the water hits near the top), breastshot (roughly central) and undershot (low down, in the bottom quarter). (2) Books on mills and hydraulics, passages read through archive.org's full-text search: A Manual of Hydraulics (1906), https://archive.org/details/amanualhydrauli00busqgoog (head-race, tail-race, sluice gate, buckets, the two cheeks or shrouds, arms assembled on the hub); Watermills of Cumbria, https://archive.org/details/watermillsofcumb0000davi (cast iron shrouds, wooden arms, wooden buckets, axle, pond, head race, wheel pit, tail race); Harnessing Water Power for Home Energy, https://archive.org/details/harnessingwaterp0000mcgu (water goes to the sluice gate, enters the flume and fills the buckets); Interpretation Program for the Van Wyck Lefferts Tide Mill, https://archive.org/details/interpretationpr00kuci (headrace, sluice gate, tailrace); The Mill at Philipsburg Manor, Upper Mills, and a Brief History of Milling (1977), https://archive.org/details/millatphilipsbur00howe (its glossary has overshot wheel, breastshot wheel and undershot wheel, in which water strikes the wheel at the bottom); Watermills (2006), https://archive.org/details/watermills0000watt (overshot, breastshot and undershot wheels). Licence: own work

The drawing: Own drawing from plain geometry; nothing traced. Licence: own work

How it works

A water wheel turns the fall or flow of water into turning power for a mill. The first view names the parts of an overshot wheel and the channels round it. The second sets three kinds side by side.

Read the full guide

The wheel and its water

Water comes from the mill pond along the headrace. The sluice gate controls how much goes on, and the flume carries it to the wheel. On the wheel, buckets are fixed between two rims called shrouds, and arms join the shrouds to the axle. The wheel hangs in the wheel pit, and the water leaves by the tailrace.

Three kinds of wheel

The kinds differ in where the water meets the wheel. On an overshot wheel it arrives at the top and fills the buckets, so its weight does the work. On a breastshot wheel it arrives about halfway up. On an undershot wheel the stream pushes the lowest part.

  • The quiz takes spokes for arms, rims for shrouds and leat or mill race for headrace.

Questions and answers

What are the buckets on a water wheel?

The boards set round the rim that catch the water. On an overshot wheel they fill on one side, which makes that side heavier, and the weight turns the wheel. They empty as they reach the bottom.

What is the difference between a headrace and a tailrace?

Both are mill races, channels for the water. The headrace brings water to the wheel from the mill pond. The tailrace carries it away once it has left the wheel.

What is the difference between overshot and undershot wheels?

An overshot wheel takes its water at the top and is turned mostly by the weight of water in its buckets. An undershot wheel dips into a stream, which pushes against the bottom of the wheel.

What does the sluice gate do?

It is a gate across the channel. Raising or lowering it lets more or less water reach the wheel, which is how the miller set the speed.

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