Hall Green Stop Lock On Macclesfield Canal - Hall Green, UK
Posted by: 
dtrebilc
N 53° 06.158 W 002° 14.966
30U E 550251 N 5883950
This stop lock was built by the Macclesfield Canal company at the point where it met the Hall Green branch of the Trent and Mersey Canal.
Waymark Code: WMQ123
Location: North West England, United Kingdom
Date Posted: 11/26/2015
Views: 5
The Canal
The Canal
The Macclesfield Canal is a canal in east Cheshire, England, one of the six that make up the Cheshire Ring.
It was the last narrow canal to be built in the U.K. and the maximum dimensions for a boat to be able to travel on the waterway are 72 feet long and 7 feet wide. The maximum headroom is 7 feet and 2 inches. The maximum draught is 3 feet and 6 inches.
The canal was built to serve the mills, mines and quarries of the Marple, Poynton, Bollington, Macclesfield and Congleton areas as well as to provide a link from Manchester to the Potteries and Midlands in competition with the Trent & Mersey, Bridgewater route.
It was completed in 1831 and reduced the distance between Manchester and the Midlands by around 25 miles.
Because the canal was one of the last built it very soon came into competition with the railways and in 1846, only 15 years later had been bought by a railway company.
It did manage to survive in commercial use but after the Second World War went into decline until the 1960s.
The canal remained popular with leisure boaters, especially as it formed part of the Cheshire Ring of Canals. It never closed and still remains popular today.
Stop Locks
A "stop" lock is a (very) low-rise lock built at the junction of two (rival) canals to prevent water from passing between them.
During the competitive years of the English waterways system, an established canal company would often refuse to allow a connection from a newer, adjacent one. This situation created the Worcester Bar in Birmingham, where goods had to be transshipped between boats on rival canals only feet apart.
Where a junction was built, either because the older canal company saw an advantage in a connection, or where the new company managed to insert a mandatory connection into its Act of Parliament, then the old company would seek to protect (and even enhance) its water supply. Normally, they would specify that, at the junction, the newer canal must be at a higher level than their existing canal. Even though the drop from the newer to the older canal might only be a few inches, the difference in levels still required a lock — called a stop lock, because it was to stop water flowing continuously between the newer canal and the older, lower one. The lock would be under the control of the new company, and the gates would, of course, "point" uphill - towards the newer canal. This would protect the water supply of the newer canal, but would nevertheless "donate" a lockful of water to the older company every time a boat went through. In times of excess water, of course, the lock "bywash" would continuously supply water to the lower canal.
When variable conditions meant that a higher water level in the new canal could not be guaranteed, then the older company would also build a stop lock (under its own control, with gates pointing towards its own canal) which could be closed when the new canal was low. This resulted in a sequential pair of locks, with gates pointing in opposite directions: one example was at Hall Green near Kidsgrove, where the southern terminus of the Macclesfield Canal joined the Hall Green Branch of the earlier Trent and Mersey Canal.
Hall Green Lock
The stop lock at Hall Green, which has a 6 inches (15 cm) fall from the Macclesfield to the T&M, was originally built as two chambers end to end, to allow for either canal to be higher. The second chamber fell into disuse when the weir level on the top pound of the Trent and Mersey Canal was permanently lowered after nationalisation to improve the air draft in Harecastle Tunnel.
Whilst the fall of the lock may appear trivial, it cannot be taken out of use (as many stop locks have), because lowering the bottom pound of the Macclesfield Canal would lead to draft problems on it (as it is a fairly shallow canal), and raising the top pound of the Trent and Mersey would lead to air draft problems through Harecastle tunnel. Indeed, as Harecastle continues to sink, the weir level may be lowered further, leading to an increased fall at this lock.
This lock has a rack of stop planks next to the top gates. These can be inserted in grooves in the canal sides to cut the flow of water. They are used when there is a leak, or repairs need to be carried out and part of the canal needs to be drained.
Stop planks are stored at strategic positions along the canal, normally next to locks or bridges because they are always built at the narrowest parts of the canal.
Normally on a narrow canal a lock has a single top gate and double bottom gates. On this particular lock this is reversed. The gates also have a ledge on them that acts as a small footbridge to give boaters access to both sides of the canal when operating the lock gates.
Waterway Name: The Macclesfield Canal
Connected Points:
The canal runs for 25 miles and 3¾ furlongs through 13 locks from Hall Green Stop Lock (where it joins the Trent and Mersey Canal (Hall Green Branch)) to Marple Junction (where it joins the Peak Forest Canal).
Type: Lock
Date Opened: 01/01/1831
Elevation Difference (meters): .00
Site Status: Operational
Web Site: [Web Link]
Date Closed (if applicable): Not listed
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