Maybe not. A syphon can only apply one atmosphere to overcome the friction per 30 ft pipe but a pump can be configured to apply more. I think their bigger problem is where to put the water as the river is full.

they should have configured all the loos in the town to be fed from the reservoir. Then if they supplied free beer to all households the natural course of things would reduce the level involving symphonic action.

they should have configured all the loos in the town to be fed from the reservoir.

Extra water supply pipes to each household? Who wants to be a plumber, Yipeeeeee.

Regards Ian.

I wondered about syphons, too, but whichever method's used the water has to be released somewhere, and that seems only to be a river already swollen, and the canal – but the latter may be effective by judicious opening of lock and side-spill hatches down-hill.

We can only watch and hope that the reservoir can be drained as quickly and safely as possible. The first need is to render the area safe enough for everyone to return home.

I would guess proper repairs will take a long time and might necessitate replacing the entire dam face.

++–

As for the town's lavatories….

I recall a former work colleague describing his parental home's arrangements in a "Coronation Street" style, Victorian housing-estate, in Leeds I think.

The necessaria at the ends of the back yards were flushed by rain-water from the roof down-spouts filling flop-jacks below the outhouse floors. Inevitably, in dry weather, down the yard had a certain, umm, ambience; whilst in wet, the place resounded with the constant " whoosh! crash! " of lots of flop-jacks all working away.

The homes including my grandparents' in Nottingham's similar Hyson Green estate also had brick outhouses beyond the tiny back gardens. Plush ones though, due to these new-fangled, high-level, cast-iron syphonic cisterns supplied from the mains water. (T'other grandparents over in Arnold were even better-off: their 1930s home's loo was indoors, off the side of the back porch.)

Apparently the reservoir was originally a supply water feed basin for the canal and lock systems. Local news info!

.

…. and that is what it remains

See my posts [yesterday] on the "What did you do … ?" thread.

**LINK**

MichaelG.

Here is one that I didn't post yesterday: **LINK**

Engineers battle through night to prevent catastrophic dam failure

[please note the publication date though]

.

I have just returned from a walk, and can confirm that even more roads in the area are closed, and there is a significant Police presence ensuring compliance !

Rain and thunderstorms are forecast for tomorrow.

MichaelG.

Siphons are a practical solution for rapid drain down in situations where it is clear there are no valve arrangements to discharge water in quantity.

A company I used to work for employed just such a mechanism to supply the transmission pumps, for circumstances when the usual draw off valve arrangements were not available (usually due to statutory reservoir inspections). Volumes could be maintained at up to 80 million litres per day via an 18 inch diameter siphon – limited by pump capacity and need to maintain reasonable suction conditions to protect the pump impellers.

If the calculation above is correct, 500 gallons/s approximates to 190 million litres per day, factor in a few losses and say 150 Ml/d should be achievable.

Compare that to the current rate of pumping – approx. 96 million litres day according to BBC (not clear whether this was the rate of pumping or the net water removed).

I suppose there are practical issues with sourcing and handling large diameter pipe quickly, but I would have thought the water companies or their contractors would have material available.

After the Rotherham dam incident, we were all told by our political masters to determine the cost of remedials to emplace rapid drain-down arrangements in critical infrastructure that did not have appropriate facilities. When the great and the good saw the cost, they turned white at the gills and ran for the hills.

As I recall we did consider siphons, but these were not put forward on the grounds of aesthetics – serried ranks of blue plastic pipe snaking over the dam was the issue, so they said…

'Tensile strength' doesn't come into it because the water in a syphon is being pushed by atmosphere, not pulled by vacuum.

Newton's Law, " an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force ". The external force is pressure. You can't be pulled by a vacuum since a vacuum is just the absence of anything. You can't pull against nothing and 'nothing' can't exert a force on 'something'.

I am rather taken with SOD's explanation for how siphons work using the analogy of a chain being dragged over an edge by gravity. ( I am sure JAs explanation using maths will be correct but I don't have the maths to follow it)

If we assume SODs explanation is a good analogy then I don't see any problem about water having nearly no tensile strength- which may well be true in general but in this case the water is in a pipe. The water has to stay in an unbroken length within the pipe because any break would cause a vacuum in any gap that formed. and air pressure on the water at both ends of the pipe would not allow that to happen- so the water behaves as if it does have tensile strength.

There is a limit though. It is well known that a siphon will not work over a "lip" of over 30 feet or so because the atmospheric pressure will not support the water column, and this may limit the use of siphons in large civil engineering situations. I am not clear how, or indeed if, siphons work in a vacuum.

Rod

Unfortunately not. Have a read of the Wikipedia article on Siphons. While it agrees Bernoulli equations provide a 'fair approximation' of the flow, the section on 'Modern Research doesn't come to a solid conclusion as to how Siphons actually work. At least not the way I read it.

It's been shown that siphons do not depend on atmospheric pressure because they work in a vacuum. Operation looks to be more to do with gravity and molecular cohesion. I wonder if anyone has tried to eliminate gravity by siphoning liquids in outer space? 

The latest research – Hughes and Gurung, Queensland University of Technology, 2014 – concluded "It follows from the above analysis that there must be a direct cohesive connection between water molecules flowing in and out of a siphon. This is true at all atmospheric pressures in which the pressure in the apex of the siphon is above the vapour pressure of water, an exception being ionic liquids." Why are ionic liquids exceptional?  Of course being Australian they were upside down when they tried the experiment…

Dave

Edited By SillyOldDuffer on 03/08/2019 18:17:16

On a similar thought can anyone explain how a hydraulic ram works ? I've seen drawings but have never seen one in the flesh so to speak

Roy