January 2014 Archives

Closing Lock Gates After Passage

It's a contraversial topic wether to “close-up” or not after working through a lock. Here are some, factual I hope, notes on the topic:

The Next Boat Through:

There is always a 50/50 chance that the next boat through a particular lock will be in a particular direction (unless boats are travelling in convoy).

This means that if you close-up, any following boat will be done a (very small) favour. A boat coming in the opposite direction will have to re-open them once more, not a favour at all; indeed they have had the gates shut in their faces.

Thus there is no net advantage to the next boat.


Barring faults, Locks leak least when left empty. That's not my opinion, but that of the Water Manager on the K&A and he should know. They leak the most when they are full with the top gate flapping unsealed.

Top gates have about three times less “seam” to leak compared to bottom and they also tend to suffer less rubbing damage. So that's why locks with a good seal on the top gate always empty on their own.

Water Saving:

The most economical usage method for a lock is to adopt a "one-up one-down" system, i.e. a following boat should wait for one in opposition. Using this method the following boat will not only save one lockfull of water, but also do the least amount of work possible as the opposing boat will work the gates, fill/empty the lock etc., etc. the downside is that it requires some patience on the part of the steerer of following boat.

Catastrophic Failure:

Closing-up should mitigate the consequences of any failure at the uphill end. Upon failure the bottom gates may be closed anyway by the onrush of water. Gates/paddles rarely, if ever, fail without human (or boat) intervention it should be noted.