How do locks work?
Going boating for the first time? Take a look at our detailed guide to locks; what they are and how they work.
What is a lock?
Locks are used to lift or lower boats from one level to another. They are found on almost all canals and rivers.
A lock is a section of canal or river that is closed off by gates which control the water level so that boats can be raised or lowered as they pass through it.
What is a flight of locks?
A flight of locks (or lock flight) resembles a flight of stairs – it consists of a number of locks (or steps) one after another. Sometimes there is a stretch of canal between one lock and the next, and sometimes the locks are so close together that the top gates of one and the bottom gates of the next are one and the same – this is called a staircase flight.
What is a manned lock?
Many of the busier locks on the Canal & River Trust's navigations have locks which are manned and operated for you during the summer months.
How do you work a lock?
Don’t worry if you are about to go on your first boating holiday and have no idea how to operate a lock, your hire boat operator is sure to talk you thorugh it before you set off. Once you get to grips with them, locks are all part of the fun of a canal holiday – and a most efficient form of exercise!
Locks have two sets of gates (top and bottom) and a chamber which your boat enters into. Crucially, locks also have openings (or sluice gates) at the top and bottom and it is by opening these that water is allowed into and out of the chamber to raise or lower the water level - and hence the boat. You and your crew will open and close the paddles using a lock handle (or windlass) which you will carry with you on your cruise.
Going up
1. Open the lock gate and take the boat into the lock. Remember to close the gate behind the boat
2. Open the sluice gate to allow the water to flow from the top pound into the lock
3. The boat will rise as the lock fills
4. Once the water level inside the lock is the same as the water level ahead in the canal, open the top gates and take the boat out
5. Remember to close both the sluice gate and the lock gate behind you to preserve water
Going down
1. Open the lock gate and take the boat into the lock. Remember to close the gate behind the boat
2. Open the sluice gate to allow the water to flow out of the lock
3. The boat will lower as the water level in the lock falls
4. Once the water level inside the lock is the same as the water level ahead in the canal, open the bottom gates and take the boat out.
5. Remember to close both the sluice gate and the lock gate behind you to preserve water
Basic principles – things to remember
Water always flows downhill and lock gates are closed against the pressure of this water. The lock gates will not open until the water pressure (level) is equal on both sides.
How long does it take?
Passing through a lock will generally take from 10 to 20 minutes, depending how big the lock is and whether or not it was originally set in favour of the boat (it is always pleasing to meet another boat coming towards you on the approach to a lock – this boat will have just exited the lock on your level and therefore the lock will be set for you).
