Energy Saving in Pump Station

Anything that is practical will respond positively to a type of analysis called the Energy Balance calculation, which is used in process plants the world over.

If it doesn't come out of the calculation, then it isn't practical. Which is useful, because one then doesn't have to build it to find out that it won't work.

to draw water from the suction side of the pump and use that water to drive turbines that drive the same pump?

No. Think about the question. Draw water from the suction side to feed the suction side?

Of course it will not work.

Thank about what you are saying.

...Would add:

Building "Perpetuum Mobile"-will never succeed....

-If you suck by pumping the same water you want to use as energy to do the sucking...

See some original Perpetuum Mobile Archimedes screw pump in a closed system...

see WIKIPEDIA

You do not get power from water. You do get power from moving water. When you take power from moving water, it moves slower. You cannot take all of the power from moving water because the water then no longer moves.

Your description of the water flow is a bit vague. It sounds like this water flow path might be an overflow path to assist in level control. If this assumption is true, then you will not get reliable water flow from this path. This might also be a diversion path for wildlife to be able to migrate. If this assumption is true then adding a turbine to this path can radically alter the ecosystem both up and down stream of this dam.

Careful planning of water flow through a dam can allow people to tame river flooding, maintain a healthy river and harvest reliable, low pollution electric power.

I imagine a dam, a penstock going to a turbine but instead of a generator there is a pump. Obviously, it is better for the pump intake to be on the high side of the dam. If the penstock had more capacity than required for the turbine, the excess could feed the suction side of the pump.

Or do I have a screwed up picture in mind.

It is not possible to tell from here.

My question is, "is it practical to draw water from the suction side of the pump and use that water to drive turbines that drive the same pump?" The flow rate of the pump is less than what the penstock can handle and what can be drawn from the dam.

Your description fits the question , misquoted by above ... other.

reading:..water from the suction side of the pump [just what is FLOWING TO the penst pump] ... [before a less-used flow to that said pump] ... The flow rate of the pump is less than what the penstock can handle and what can be drawn from the dam.

[Then ] and use that water to drive turbines that drive the same pump?"

YES: IF sufficient water is available to overcome ALL necessary ENERGY BALANCE of "turbines" to "direct" power coupling to the first mentioned "pump"...

I have reason to presume

"A picture is worth a thousand words" - Anon.

Is this going to be one of those threads where another few hundred words in a couple of dozen replies is to transpire before a single sketch drawing gets posted?

Probably there will never be any drawing ever provided.

A possible insight to this stalling discussion that I'd like to remind people is that the Roman aqueduct system moved vast quantities of water up and down hills without the use of an electric motor.

From where I see it, your proposal should be given greater investigation.

There are available "in line" energy recovery turbines that can also perform the work of PRV's. (They are actually sold as PRV systems with the benefit of "scavenging" the energy that is normally dissipated.) We are in the process of this very same investigation for our water processing facility at 20ML per day.

Your use of the phrase "draw water" might have distracted some readers. I understandthat you have a delivery pipe from the dam and have an outlet available that is upstream from the pump inlet, but you strongly assert that there is excess supply available.

If that is the case, then a parallel water stream driving a turbine of some description also seems possible. (Note the efficiency would not be as good as a purpose designed system and there might be better long term economic benefit in doing this properly.)

I would not consider "direct coupled" turbine and pump.

Are you currently creating energy at that dam?

I suppose you can make an installment of a turbine at the dam similar to what wiki shows, http://en.wikipedia.org/wiki/Penstock

If it is just about pumping water you might consider this: http://en.wikipedia.org/wiki/Hydraulic_ram

Not sure these exists for larger scale projects.

just gotta ask:

can you also save any energy/money using any (if available) cool water to directly cool your office without an air conditioner, too?

No! And hence you asked: In Winter when you do not need air-condition you ain't save nothing!