A Beginners Guide to Canal Boating 
- Locks, bridges,  aqueducts & tunnels -

This page last updated on 20/02/2000
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Unfortunately for the canal engineers, the routes the canals needed to cover to enable goods to be more easily moved from town to town were not always along level ground (which is obviously needed for an artificial  watercourse without an unending supply of water, particularly if you don't want to have a strong current in places and waterfalls in others. Also landowners and the general population still needed to be able to make their way across the new waterways. This led to a need for BRIDGES for access,  LOCKS to go up and down hill, AQUEDUCTS to cross valleys and TUNNELS to avoid unnecessarily building locks to climb and descend hills.

Locks

Locks are perhaps the thing about canals that scares people who have not visited the canals the most, but in truth they are a simple idea gracefully executed, and take very little skill and only a minimal amount of strength to operate. Having said that, DO NOT take them for granted. They are perhaps the most dangerous thing on the canals if not given the respect they deserve.

When the original canals were built great care was taken when surveying the route to minimise the need for locks. This was due to the extra time it made the journey take to work through a lock, and also the water each lock used. Each lock may use as much as 90,000 gallons of water depending on its depth and width. This all has to be replaced which often meant building vast reservoirs where natural sources were not available. Now, the visiting boater looks on them as a challenge and an interesting diversion from the gentle cruising along. 

The time taken to work through a lock? Well this varies tremendously. A single narrow lock set ready for you on your arrival (water level correct for your direction of travel) may take 5 minutes to work through, set against you maybe 8 minutes. For wide locks you might add an extra 2 to 3 minutes. Staircase locks, particularly if operated by the lock keeper, can be much quicker. I have been helped through the 10 staircase locks at Foxton in 31 minutes. These times all assume a reasonably adept crew, and no holdups because of a queue of boats waiting to use the locks. On an average holiday, with a reasonable mix of lock types I expect to do an average of 6 to 7 locks an hour with just one crew member, but for the novice, it is perhaps more realistic, particularly when planning how far you will travel, to assume 4 locks an hour.

Here I hope to give you an overview of "locking skills" which will help you to feel confident when you first meet with one. Do not worry though, if you hire a boat you will be given full instructions and a demonstration of how they work before you are left to your own devices.

What is a Lock?

Basically it is a method of raising or lowering your boat from one level of water to another, and it can be likened to a "giant bathtub". Working your boat through a lock involves getting your boat into the "tub", changing the level of the water in it by use of the "taps" and the "plug" and then getting your boat out again. 

 Locks come in various sizes, but the main difference is the width, they are either narrow and will only take a boat up to a nominal 6ft 10in width or wide, when they will in theory take two side by side or one wide beam boat. The lengths also vary depending on which canal you are on. The principle behind the operation is however the same whichever size they are. 

At each end of the lock there will be a gate or gates, this depends on the width of the lock and also when the canal was built and by whom. This is the method used to get your boat in or out of the lock chamber (the bath tub)

The "taps" and the "plug" are the paddles, trapdoors which you open and close so letting water in or out. They are the taps when filling the lock and the plug when emptying it. You have paddles  at both ends of the lock. At the higher level, they form the taps, at the lower level the plug.

There are two types of paddle, gate and ground. Gate paddles are situated in the actual gate, and ground paddles are fitted to underground culverts running between the chamber of the lock and the canal. At some locks (particularly wide locks) you will find you have both at each end. More commonly, you find gate paddles at the lower level end and ground paddles at the higher level. 

How do I work a Lock?

The secret to operating a lock successfully is the same as using a bath. If you are trying to fill it, make sure the plug is in before turning on the taps (bottom paddles closed before opening the top paddles) If trying to empty it, turn off the taps before pulling the plug out (close the top paddles before opening the bottom paddles)  Of course, whether trying to fill or empty a lock you first have to ensure the gates at both ends are closed. When a lock is referred to as empty, it does still of course have water in, otherwise you would not be able to float your boat out. What is actually meant is that the water in it is the same level as the water at the lower level of the canal. The same applies for when saying full, the lock may not be full, it just means that in this case the level now coincides with that at the higher level of the canal.

Steps in working a lock

Things to be careful of....

• Keep an eye open for other people doing silly things.

• Look out for signs giving specific local instructions for use of the lock.

• Ensure you only have paddles open at one end at a time.

• Keep the boat toward the bottom gate, especially when going down as there is a cill protruding into the lock which the top gate rests on which you may get caught up on.

• Beware of the boat getting caught up on any protrusion from the side of the lock chamber, keep side fenders up when using a lock otherwise they may jam.

• Do not leave the windlass on the paddle spindle in case it slips.

• Wind down the paddles so you avoid damage.

• When opening and closing the gates always stand on the landward side of the balance beams.

• Never close a gate by opening the paddles (using the force of the water flowing into or out of the lock) this will slam the gate hard risking damage to the gate, and anyone in the way of the balance beam.

• Always make the safety of the boat and crew your main concern - keep an eye on what is happening at all times. If anything does go wrong you can stop things by closing all paddles.

• Beware of operating paddles too quickly to fill a lock, this can cause a strong draw forward  on the boat and cause an accident - open part way and wait for the boat to settle before continuing. If necessary use reverse gear to help steady the boat or even take a rope ashore and pass round a bollard.

• Be careful of top gate paddles when going up in a lock, the opening for these is often above the water level, and there is a danger of flooding the boat.

• Never tie your boat to a bollard while in a lock, if you wish you can pass it round one, but you should always have it attended by a crew member to avoid the boat getting hung up as it goes down.

• Don't leave your windlass behind !! you will need it again at the next lock.
  

The main thing with locks, as with canal boating in general, is to take your time. Locks have their own natural rhythm, and cannot be hurried.  Trying to push open the gates before the waterlevels are equalised is fruitless. Even half an inch difference will be too much to overcome. Boaters are friendly folk in general, and will usually offer to help with a lock if they are there at the same time as you. Most are responsible, and will ask you before opening a paddle, especially if they know you are fairly new to the canals. Some however are in a hurry, or assume you know what will happen and just open the paddles as fast as they can. Remember, If your boat is in the lock YOU are in charge.  If you remember the bathtub analogy and also take your time, you will not go far wrong. 

All the above applies to any lock, but there are some differences worth pointing out regarding Wide locks and Staircase locks.

 In wide locks, especially when going up, your boat may well get buffeted about by the water flow if you are the only boat in the lock. To help avoid this keep the boat to one side of the lock by the use of  ropes ( but hold it - do not tie it firmly) and if going up, open the paddles on the same side as the boat first.

Staircase locks are used where the canal meets a steep climb. They differ from normal locks in that the bottom gate of one lock forms the top gate of the next with no canal between. They are very often manned by a lock keeper as they have a slightly different method of operation. If so follow his instructions. Otherwise look out for local signs giving specific instructions.  If there are none using  the following procedure will work safely. The first thing to remember is that in a narrow staircase you cannot pass another boat, so wait until your way is clear before starting.  It is imperative to remember that as you empty water from one lock it will go straight in to the next, so this needs to be empty ready for this, otherwise the lock will overflow, and may cause an accident or at the least damage the towpath. You must therefore "set" the locks* before starting to travel through them as opposite. If there are more than two in a staircase it may well be necessary to empty and fill the same lock several times in order to get the levels right in all the locks. * The exception to this is if side ponds are in use. Here the water is run into a holding lake by the side of the locks to conserve water. Special instructions will always be given for their usage as extra paddles are needed compared to a normal lock.

Refer to single handed boating for now, for more information on this

Bridges

Bridges were obviously built to allow traffic of one sort or another, to pass over the canals. The variety in them is enormous. Ranging from new structures carrying motorways over them to a bridge just to carry a footpath across. The design is also something to behold, from purely functional - to get a farmer and his stock from one side to the other, to wildly ornate - often the "price" extracted by a local land owner to bring the canal across his land was a decorative bridge. 

Although canals generally even where locks are narrow, are 40 to 50 ft across, the cost of building bridges meant that most bridges were built on an artificial narrowing of the canal to be just wide and high enough to allow the boats to get through. so care is needed when navigating them as you will often only have a foot or so of clearance to the side and maybe not much head room, so crew should be moved from the roof before going under a bridge. The canal builder also had a great sense of humor and built many bridges at bends, so it is necessary to keep a look out for on coming boats and give way as necessary. 

Bridges are a good place to spot the signs of bygone days when boats were horse drawn. On the towpath side of the bridge metal strips will often be found with groves worn into them by the ropes used to pull the boats. You may also notice a "slot" cut in the stones either side of the canal which form the bank. This is used to drop "stop planks" into to form a dam if for any reason part of the canal needs to be drained. To complement this, you will often see small tunnels in the side of the bridges, or small low huts at the side where the planks are or were stored.

On some canals, notably the Southern Oxford and the Leeds, Liverpool, instead of stone structures a cheaper moveable bridge was used which crosses the canal barely above the water and which you need to move in order to pass by.  The basic forms of these are pictured opposite. A lift bridge, where by pulling on a rope or chain attached to a balance beam you raise the bridge. Or the swing bridge, where by pushing against a balance beam you swivel the bridge out of the way. Like locks both come with many variations to the basic theme, but usually it is just muscle power that  is needed to overcome the obstacle. The exceptions to this are bridges which take a lot of traffic (some are even found where main roads cross canals) Here you may have railway like gates to close across the road to halt the traffic, and because of the more substantial nature of the bridge it may be necessary to either use a windlass to employ a hydraulic movement or in some cases they are even electrically powered. In most of these exceptions you also need a British Waterways standard key (one will have been supplied by your boat yard) to unlock the mechanisms to prevent children tampering. You will always find instructions posted for this type of bridge. The main things to remember when using these moveable bridges, either human or mechanically operated, is that you should always leave them in the position you found them (open or closed) A farmer may have a particular reason for leaving one open or find himself stranded if you do not return one to the closed position, and be courteous to road traffic you may meet. Also do not be tempted to think that once you have got a bridge in an open position you can leave it that way unattended while you pass below, the retaining mechanism may just be the weight you have employed to open it. (see my page on single handed boating) And finally, the clearance for your boat when the bridge is moved may be very limited so it is important that crew members are aware of the danger and keep arms and legs within the boat.

Tunnels

Tunnels are often built on the summit levels of canals (where in both directions the canal falls through one or more locks.) The reason behind building what was at the time probably the most difficult and costly structure (both in cash and lives of the workers) rather than continuing with the locks up and over the hill was the need to save water (each lock takes up to 90,000 gallons) and also to provide a long level summit section which by digging it a little deeper than perhaps necessary would be able to act as a reservoir to supply some of the canals needs. Further reservoirs were often built on the surrounding hills to supplement this. Some tunnels were also built purely to overcome obstructions to the canal without having to make detours or build extra locks which again would need a supply of water.

Tunnels vary in length from a few yards which look much like a large bridge, to ones at over 3 miles long. They also vary between being wide enough to allow boats to pass, or suitable for only one way traffic. It is the width  that presents the problem with tunnels. If one way traffic is all it will accommodate, then delays are often caused while you wait for the tunnel to be clear in the direction you wish to travel. Indeed in some cases such is the length of the tunnel it becomes necessary to have timetabled journeys in each direction. 

Whether wide or narrow navigating a tunnel of any length is a strange business, with only the lights of your boat to illuminate your way. this leads to the possibility of scraping the boat against the sides and roof of the tunnel if care is not taken. All tunnels have safety instructions posted at each end.  

Aqueducts

Aqueducts are if you like the opposite of bridges. They are a structure that takes a canal over an obstruction which is at a lower level than the course of the canal. This usually happens when a canal changes sides in a valley, but does occasionally happen elsewhere. The aqueduct may cross a stream, a road or just the valley floor. They vary in size from almost literally a hole taking a large pipe carrying a stream beneath the canal to the simply spectacular such as the World Renowned Pontcysyllte Aqueduct at Trevor near Llangollen in Wales. This magnificent structure, built by Telford in 1805 is over a 1000 feet long and at its highest 127ft above the ground.

Truthfully the only problems they provide is that most of the substantial ones will only allow traffic in one direction at a time, and if you dislike heights, you may prefer to stay inside your boat while crossing ones like The Pontcysyllte.