Locks, another thought

[Ricco1]

Following on from my other thread I've been giving the whole process some thought.

 

My understanding is that generally, if no other boats are around, a boater should leave a lock with both gates closed and paddles down. OK so far?

 

Now then, and assuming no other boats are in sight: if a boater is single handed he or she needs to stop and tie up after the lock in order to close the gate. If the boater were to leave the gate open: If the next boat along is coming in the opposite direction it can motor into the lock without opening any gates at all. If the next boat is following in the same direction the crew would need to close one set of gates and open another. So the effect of doing this would seem to be neutral to other boaters, but saves the single handed boater needing to stop and tie up so often.

 

I don't do this as I'm not sure it's acceptable, but thought I'd put it out there for comment by more experienced boaters.

[Thorfast]

This has been discussed many times on this forum.

Some people say leave gates open as you leave, many say close them.

Except where there is a sign to say leave a set of gates open, CRT guidance is to close them.

[WJM]

Closing gates behind you only ever increases the overall workload for everyone.

[Paul C]

Its come up before!!!! Worth a search for the main debating points.

[billS]

Closing gates behind you only ever increases the overall workload for everyone.

 

And indeed wear and tear on the infrastructure and your boat gearbox. I much prefer the system on the Wey where the navigation authority instruction is to leave the gates open behind you.

[Naughty Cal]

We leave them open unless there are signs saying to do otherwise or the gates leak excessively.

[nicknorman]

Gates on canals should always be closed (I can't think of any signage where it says to leave open, but perhaps there is). Yes this may increase workload a bit but if you want minimum workload I suggest staying in the marina. The reason for doing it is to conserve water. People may think they can assess the leakage rate but they can't, as it also depends on how long til the next boat comes, something you don't know. We have personally had delays of many hours caused by drained pounds caused by people being too lazy and selfish to close the gates.

 

On canalised rivers there is not a water issue and gates can reasonably be left open.

 

Bottom line is that if you leave gates open on a canal, you are selfish and lazy and nearly everyone else will think you are an arse.

[RLWP]

Just shut the gates

 

Richard

[gazza]

Nah, Leave em open

[RLWP]

Nah, Leave em open

 

I'm quite happy to do that, just as soon as CRTs advice is to do it. When everyone does the same, there's no problem. It's when someone thinks they know better and do the opposite that trouble happens

 

Richard

[billS]

Gates on canals should always be closed (I can't think of any signage where it says to leave open, but perhaps there is). Yes this may increase workload a bit but if you want minimum workload I suggest staying in the marina. The reason for doing it is to conserve water.

 

That will only be true in cases where the top gates leak faster than the bottom gates.

 

That appears to be quite a rare scenario. I see many locks which when full leak to empty, but relatively few which when empty leak to full.

Edited July 6, 2016 by billS

[Naughty Cal]

 

That will only be true in cases where the top gates leak faster than the bottom gates.

 

That appears to be quite a rare scenario. I see many lock which when full leak to empty, but relatively few which when empty leak to full.

Bardney Lock.

 

ETA: The only lock we usually leave the gates shut on in our local area.

Edited July 6, 2016 by Naughty Cal

[RLWP]

 

That will only be true in cases where the top gates leak faster than the bottom gates.

 

That appears to be quite a rare scenario. I see many locks which when full leak to empty, but relatively few which when empty leak to full.

 

Hatton top lock

 

Richard

[magpie patrick]

 

That will only be true in cases where the top gates leak faster than the bottom gates.

 

That appears to be quite a rare scenario. I see many locks which when full leak to empty, but relatively few which when empty leak to full.

 

Having spend seven weeks moored at Great Haywood, the lock there seems to do it, and yet there is no obvious leakage. It must be coming under the cill or something. It's a long level to drain because it included Tixal Wide, but I bet the lock left unattended with bottom gates open for a day or so would have the level down a foot or two

[billS]

Exactly - the few exceptions to the rule are unusual which is why you can remember them.

 

One lock on the Hatton flight leaks full - how many leak empty?

[nicknorman]

Bardney Lock.

 

ETA: The only lock we usually leave the gates shut on in our local area.

That is on a canalised river. Your local area locks are all canalised rivers I think? As I said, in canalised rivers there is no reason not to leave the exit gates open, unless signs to the contrary for flow reasons (eg river nene, all to be left empty.)

[gazza]

 

I'm quite happy to do that, just as soon as CRTs advice is to do it. When everyone does the same, there's no problem. It's when someone thinks they know better and do the opposite that trouble happens

 

Richard

 

Good excuse for getting the handbags out though

 

For me, without being mischievous, it is, as you say, shut unless signed otherwise - it goes without saying leave em open if you can see a boat coming in the opposite direction.

Our locks have lovely A4 notices and plenty of gert big stickers requesting the locks are left with the gates closed and the guillotine gate lifted, doesn't stop ignorant arses ignoring them though!

[magpie patrick]

Exactly - the few exceptions to the rule are unusual which is why you can remember them.

 

One lock on the Hatton flight leaks full - how many leak empty?

 

But the point is (certainly at Haywood) that you can't see that it will do this, so the casual visitor can't know to make an exception here and close the gates

[churchward]

 

That will only be true in cases where the top gates leak faster than the bottom gates.

 

That appears to be quite a rare scenario. I see many locks which when full leak to empty, but relatively few which when empty leak to full.

Not really. There are many locks that will leak or fill to about half full. The lock leaks when there is most pressure (when full) and in any case the leak outlet is not always at the bottom of the lower gates but somewhere higher up. It follows in that scenario that leakage will be kept/slowed to a minimum when all the gates are closed. This scenario is not rare.

[Laurie Booth]

Just shut the gates

 

Richard

Ditto

[billS]

 

But the point is (certainly at Haywood) that you can't see that it will do this, so the casual visitor can't know to make an exception here and close the gates

 

That's true. However, if it was accepted practice that gates were left open, then these exceptions could be dealt with by local notices on the locks, like the ones which ask for certain locks to be left empty to avoid flooding the basements of adjacent properties.

 

Not really. There are many locks that will leak or fill to about half full. The lock leaks when there is most pressure (when full) and in any case the leak outlet is not always at the bottom of the lower gates but somewhere higher up. It follows in that scenario that leakage will be kept/slowed to a minimum when all the gates are closed. This scenario is not rare.

 

If a lock leaks to half full, then an equilibrium is reached where both gates are leaking at the same rate -the rate of leakage of the top gate. Closing the bottom gates does not change that. I guess you could argue that you save half a lock of water if the next boat coming through happens to come from above the lock.

[Machpoint005]

 

That's true. However, if it was accepted practice that gates were left open, then these exceptions could be dealt with by local notices on the locks, like the ones which ask for certain locks to be left empty to avoid flooding the basements of adjacent properties.

 

 

If a lock leaks to half full, then an equilibrium is reached where both gates are leaking at the same rate -the rate of leakage of the top gate. Closing the bottom gates does not change that. I guess you could argue that you save half a lock of water if the next boat coming through happens to come from above the lock.

 

This includes the case where neither set of gates leaks once the lock is half empty. You have then lost half a lockful of water and that's all.

[cuthound]

Good God Ricco1, leaving lock gates open is almost as contentious a subject as boat toilets...

 

The main advantage is the time saved, the main counter argument is the increased loss of water as more water leaks through one set of gates than two.

 

Interestingly, in the working days, all boaters left the exit gates open and paddles up.

[nicknorman]

If a lock leaks to half full, then an equilibrium is reached where both gates are leaking at the same rate -the rate of leakage of the top gate. Closing the bottom gates does not change that. I guess you could argue that you save half a lock of water if the next boat coming through happens to come from above the lock.

 

This is not true. The rate of leak is roughly proportional to the pressure ie the water level difference. If the lock leaks to half full, the leak rate at each gate is half what it would be if one gate was left open. And the leaks are "in series" so the overall leak rate is halved. However leaks are not always as simple as that, sometimes a leak only occurs at a certain level of the gate which may or may not stop at 1/2 level. But overall shutting both gates will reduce the risk of a severe leak. Also we quite often seem to find paddles not fully wound down. If gates a left open with paddles at the other end not fully closed, there can be a significant waste of water and lowering of pound levels.

 

Bottom line, as I have said repeatedly, is just shut the gates on canals as per the Boater's handbook and the many signs on lock flights. Or if you are a lazy arrogant arse who knows better than everyone else, then leave them open and be hated by all.

[billS]

 

This includes the case where neither set of gates leaks once the lock is half empty. You have then lost half a lockful of water and that's all.

 

I don't think that is a realistic scenario. A leak in the top gates would have to be extremely small for it to be stopped by a small change in hydrostatic pressure. If the lock were filled to say, 2 feet above the top cill, then that would only give a pressure difference of about 0.9 psi compared with an empty lock. Any leak which could be stopped by that would be very small.