Whaley Bridge pumps...

[Jim K..]

Perhaps it's your experience that's lacking...

[Tim+]

Why not syphons? I mean, pumps use power, quite a lot of it and are relatively expensive. For a syphon, you just need a suitably sized bit of pipe.

Tim

[Jim GM4DHJ ...]

and sook really hard ....

[Steve Walker]

I'd hate to have to suck on the end to get it started ;)

Seriously. Yes, I would have thought siphoning from behind the dam, over the top and down to the bottom would make sense. Even if it wasn't as effective as pumping, it could surely supplement it.

SteveW

[newshound]

You've already said it: suitably sized.

I don't know how far they need to deliver the water, but the flow rate is dependent on the frictional losses. The pumped system still recovers available potential energy. To get the same flow rate from a syphon will require *much* larger hoses, especially if they are long.

[NY]

I suppose they would still need a pump to "prime" the syphon, and it would have to remain "in circuit" afterwards, because would be very difficult to remove safely when there's a lot of water flowing, and an unpowered pump may significantly reduce the possible flow rate. It also depends on there being a significant head of water between the inlet point and the point where it discharges into the spillway after going over the "hump" between reservoir and spillway.

I wonder whether the power needed to drive the pumps does decrease once water is flowing and syphon conditions exist, or whether it is substantially the same no matter if the outlet is at the same level as the input or if the output is a lot lower than the input.

[Steve Walker]

The videos show them pumping into a nearby river very close to the dam. Presumably some would only need getting to the bottom of the dam and would go downhill from there anyway. In either case, the hoses would be fairly short. Even if it couldn't replace pumping, it surely could supplement it.

SteveW

[Chris Hogg]

A submersible centrifugal pump on the front end would get it started, then once the syphon is going, you just switch off the pump and leave the syphon to work.

[Steve Walker]

You can start a syphon by placing the whole pipe in the water, letting it fill, closing a valve on the end, lifting the end over and down and opening the valve. A job for a mobile crane.

If the outlet were placed at the bottom of the dam, there would be a decent head until the reservoir was virtually empty.

Even if the flow were not as great as with the pumps, more syphons could be used or they could be just used to supplement the pumps and drain the reservoir faster.

I would presume that the syphon effect would assist the pumps, at least be reducing the back pressure and counterbalancing frictional effects.

SteveW

[newshound]

You probably don't want to be driving a mobile crane on the top of the dam.

Yes it *could* be done with a Chinook and a lot of men on top of the dam.

In the big scheme of things, fire engines have the pumps and hoses and experienced staff. A few thousand gallons of diesel is neither here nor there.

[Richard]

Good luck syphoning at the rate the pumps have been working.

[Jim GM4DHJ ...]

I got dragged into one of these years ago...under the building scotland act a small dam is a dangerous building believe it or not....I didn't.....

[Gareth's was W7 now W10 Downst]

You also need an arrangement to start the siphon, which for the scales under discussion mean a valve or tap at both ends of the pipe, and a removable cover at the top of the siphon through which the whole caboodle is filled with water.

[Dave Liquorice]

The Fire and Rescue service high volume pumps are part of the national reslience system. Seems there are 51 dotted about the country to be called upon locally or nationally as required. Each one is capable of delivering 7,000 litres per minute (enough to meet the demand of up to three fire engines all running flat out) over several km of hose. They are floating "sump pumps", the small red boxes in the water in some of the pictures. Seen reported that 16 of these are in use. The same pictures also reveal larger yellow pumps, presumably commercial pumps of even higher capacity.

The coverage of these "technical" details is sadly lacking. Most people won't have any idea of the size of pipes and speed of flow that shifting that volume of water requires.

And some means of priming it and some means of keeping the inlet clear enough of the bottom to stop it sucking that up and some means of shutting it off without needing to reprime. Shutting off if the outflow starts to cause damage at the discharge point of whatever is being used to carry the flow starts to flood further down stream due to local rain.

[Brian Gaff]

Yes but its really low pressure and if you want to move a lot at a time there is no benefit to using a siphon. Incidentally, where ARE they putting all that water? Brian

[Brian Gaff]

At what level will they be able to check things out as to integrity etc? I feel sorry for all the probably dead abandoned pets, so I'm just waiting for the court cases to start. Brian

[Brian Reay]

It depends where they are moving the water to. When the story first broke (no pun intended) I looked at the area on Google maps. I doubt they are moving the water to below the damn- based on the area and what I? d heard on the news. They seem to be diverting water which normally flows into the lake behind the damn and pumping it out into rivers in the area.

Siphons require a ?drop? or ?head? which, especially as the level drops, probably won?t exist on the high side of the damn.

[tony sayer]

And it can only be supposed that the river their pumping into is at or near capacity?..

[jrwalliker]

A lake near here was drained a few years ago for maintenance of its dam. They used two siphon hoses each about 15cm diameter and it took about two weeks.

Each hose had a strainer at the sucking end. I don't know how the siphons were started, but they kept going happily until the lake was nearly empty.

John

[The Natural Philosopher]

you can't siphon up more than 32ft