Narrowboating Guides-Canal Locks
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Wed Nov 20, 2013 at 3:12pm

What are Canal Locks

Locks are a mechanism buit to enable the canal to go up or downhill by altering the level of the water of the canal. There are several different types of locks, but the usual type on a canal is a pair of hinged water tight gates which close together in a V shape with the V pointing uphill. The pressure of the water helps to close the V shaped gates tighter so that less water can leak. Narrow locks often have a single gate that closes against a frame. The principle is the same whatever type of lock. The water tight gates open at each end into the sluices which are known as paddles on the canal, with a chamber in between. A flight of locks consists of a number of locks in a row, sometimes they are next to each other, this is called a staicase, and sometimes there is a section of canal in between each lock. A windlass is a lever used to turn the cogs which wind the lock paddle up and down in order to open or close the lock.


The bottom lock at Whilton Locks also known as the Buckby Flight on the Grand Union Canal
two canal boats going through the locks


At Whilton Locks on the Grand Union Canal just outside our marina there is a flight of thirteen locks, pictured above.

How to Use A Canal Lock 

To go uphill- If the lock is full you should check that no boat is approaching from up the canal. If they are the rule is that you should let them go through the lock first. This conserves water and saves time overall. Empty the lock by raising the lower paddles, check that the top paddles have not been left open. If they are even slightly open the lock will not quite empty. When the lock is empty and the bottom gates are open bring the boat in by slowly lining the boat up as straight as possible. This takes some time to practice but don't panic and take it slowly, you will soon get used to manouvering the boat in and out of locks. Do not get too close to the gates once in the lock, bring the boat to a stop and close the lock gate behind you. Open the sluice gate to allow the water from the top pound to flow into the lock chamber. The boat will rise slowly as the lock fills. Once the lock is full and the water level is the same as the canal ahead open the top gates and move the boat out of the lock. Close the sluice gate and the lock gate behind you. To go downhill reverse the procedure. 

Remember that water always flows downhill and the lock gates will not open until the water pressure is even on both sides. Going through a lock will take you between ten and twenty minutes, depending whether or not you have to wait and whether the lock was on your level to begin with.