Canals and leaky lock gates

[eMeS]

I watch far too many TV programmes about canals; and almost inevitably, the programme makers tell us how important a good supply of water is for any canal, and then show us locks with leaking gates etc. But what I've never seen is any attempt to use a modern material (such as tough rubber or plastic) to help leak proof a lock gate which is worn or somewhat out of shape. Surely, if the problem is as bad as claimed, it would be worth applying some modern technology to the problem - or would that destroy the image of travelling back in time?
Sadly, when I've been on a canal holiday, rain has been plentiful, and a dry day would have been very welcome.

 

[birchesgreen]

They do replace lock gates when the leak gets too bad (though by "bad" it seems to be basically gushing out). You could probably make better gates which aesthetically didn't look much different, its probably down to money which British Waterways don't have a lot of!

 

[High Dyke]

Oddly enough I was walking a section of the Grantham Canal on Monday afternoon. Whilst the particular section I walked hasn't been restored yet it should still contain water. However, signs provided by the Canal and Rivers Trust explain they are aware of the low water level, but don't really know how to resolve it. The section in question, a 2 mile portion from Hickling Basin, doesn't have any locks in that area. Elsewhere along the 33 mile route then it has dried up - partly due to subsidence around the site of the (former) Cotgrave Colliery.

 

[John Webb]

From some years of canal cruising (although not recently) and still reading waterways-related magazines, I understand the reason why it's not easy to add modern technology to traditional lock gates is two-fold:
(a) some form of flexible seal added to the wood would be more susceptible to damage from boats entering or leaving the lock; once damaged it would leak more than the wear and tear on the wood alone would;
(b) more susceptible to deliberate damage by vandalism with the same result.

 

[Belperpete]

Most canals have a constant flow of water along them, to make up for differences in lock sizes and natural losses. There is usually a channel running parallel to the lock carrying flowing water. In many cases it is underground, but if you know where to look you can see the inlet and outflow. I suspect that leakage through lock gates is insignificant compared to this constant flow, unless really bad.

 

[eMeS]

Most canals have a constant flow of water... ... In many cases it is underground, but if you know where to look you can see the inlet and outflow. I suspect that leakage through lock gates is insignificant compared to this constant flow, unless really bad.

I wasn't aware of hidden water flows as described above, being common, so that probably does explain what we all see.

 

[John Webb]

Most canals have a constant flow of water along them, to make up for differences in lock sizes and natural losses. There is usually a channel running parallel to the lock carrying flowing water. In many cases it is underground, but if you know where to look you can see the inlet and outflow. I suspect that leakage through lock gates is insignificant compared to this constant flow, unless really bad.

I wasn't aware of hidden water flows as described above, being common, so that probably does explain what we all see.

Most locks have a 'bypass' which channels surplus water from the upper level into the lower level to keep water levels constant - or in the case of the Llangollen Canal to help carry water to the Hurleston Reservoir from whence it is distributed to other users. Some of these bypasses (called by-washes in some parts) are open channels, some are underground. There are wide variations in design; the worst are those which discharge into the canal close to the lower gates and set up a cross-current which makes a smooth entry to or exit from the lock near impossible!

(I have a vague recollection of being on the Shropshire Union where a sheep had fallen into the open bypass channel and we helped the farmer recover it by adjusting the level in the lock so the back of our boat was on a level with the lock-sides so the farmer could get the sheep from one side of the lock to the towpath side to take it back to his farm!)

 

[Doctor Fegg]

Should you ever have half an hour to kill at Manchester Piccadilly, go down to the Rochdale Canal and have a look at the bywashes past the locks there. The Rochdale can have a really significant flow after heavy rain - not surprising given that it runs down from the Pennines. The locks from Piccadilly down to Castlefield, known as the "Rochdale Nine", have inadequate or non-existent bywashes, so the water just weirs over the lock-gates instead. It's quite a sight, and it also makes the gates piggishly difficult to operate!

 

[eMeS]

Should you ever have half an hour to kill at Manchester Piccadilly, go down to the Rochdale Canal ...

That brings back memories - brought up close to Manchester and when it was "London Road", I remember when the Rochdale Canal was unusable, and marvelling how good the canals were in central Birmingham when we travelled through in 1956, in a modified WWII-surplus pontoon.

 

[John Webb]

Should you ever have half an hour to kill at Manchester Piccadilly, go down to the Rochdale Canal and have a look at the bywashes past the locks there. The Rochdale can have a really significant flow after heavy rain - not surprising given that it runs down from the Pennines. The locks from Piccadilly down to Castlefield, known as the "Rochdale Nine", have inadequate or non-existent bywashes, so the water just weirs over the lock-gates instead. It's quite a sight, and it also makes the gates piggishly difficult to operate!

I think the Leeds and Liverpool canal is another one where some locks don't have a by-pass and the gates are designed to allow surplus water over the top of the gates.

 

[satisnek]

Leakage is often a problem at 'wide' locks (i.e. those which can accommodate two boats side by side) as a result of opening just one gate when there's only one boat using the lock. Contact with the edge of the closed gate when passing through is often unavoidable and causes this edge to wear away. I would guess that this would happen regardless of the material used and BWB/CRT may well have experimented with different materials in the past.

It can become particularly bad on bottom gates, to the point where, when going up, it's impossible to open the top gate(s) unless ALL paddles are wide open (you can't close the paddles on the other side first then come back across to open your gate).

Guilty as charged...

 

[Doctor Fegg]

I would guess that this would happen regardless of the material used and BWB/CRT may well have experimented with different materials in the past.

They have. There was a period in the 90s/early 2000s when they were using African hardwoods like ekki and opepe. These days they've reverted to oak, often from Pontrilas I think.

CRT sometimes open up their lock-gate workshops for Heritage Open Days in September. Very much worth going to: I visited Stanley Ferry a decade ago for a Waterways World feature and it was fascinating. (The other workshop is Bradley, near Wednesbury.)

 

[eMeS]

...
CRT sometimes open up their lock-gate workshops for Heritage Open Days in September. Very much worth going to: I visited Stanley Ferry a decade ago for a Waterways World feature and it was fascinating. (The other workshop is Bradley, near Wednesbury.)

I remember going round the lock gate works at Bulborne (not far from Tring) decades ago. Is it still there?

 

[John Webb]

I remember going round the lock gate works at Bulborne (not far from Tring) decades ago. Is it still there?

The buildings are still there (click on photo to go to the larger original):
Bulbourne canal works

© Copyright Mark Percy and licensed for reuse under this Creative Commons Licence.
But I think the Canal and River Trust no longer use them. I recall reading a while ago that lock-gate making was now concentrated in two workshops, but I can't remember which ones.

 

[Doctor Fegg]

Bulbourne hasn't been a lock-gate workshop for a long time - early 2000s IIRC.

The two CRT workshops still in use are Stanley Ferry near Wakefield, and Bradley near Wednesbury. There's several independent manufacturers, some of which specialise in steel gates (common on the Thames) or composite. I believe that Hargreaves Lock Gates, the former Rochdale Canal workshops at Callis Mill, has ceased operation in the last few years.