Caisson lock

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Caisson lock" – news · newspapers · books · scholar · JSTOR (March 2022) (Learn how and when to remove this message)

The caisson lock is a type of canal lock in which a narrowboat is floated into a sealed watertight box and raised or lowered between two different canal water levels. It was invented in the late 18th century as a solution to the problem posed by the excessive demand for water when conventional locks were used to raise and lower canal boats through large height differences. Such locks, each of which would only raise and lower boats through small height differences of a few feet, would not suffice when large height differences had to be tackled nor when water was in short supply. The caisson (or caisoon) was thought to be one solution, although it transpired that the technology of the day was not capable of achieving this type of construction economically.

It was designed primarily as a water-saving measure, and also was an attempt to minimise construction costs compared with other engineering solutions of the time. In use it was capable of replacing up to seven conventional locks.^[1] Other design benefits were speed of boat descent/ascent, and only a little loss of water when operating compared with a conventional boat lock.