Backyard Aquaponics
A place to discuss aquaponics

If you pump water from a sump to some solar piping on a garden shed roof (2m Head) and the return pipe comes back to the sump does the returning water (siphoning) make it easier on the pump?

I would only think it would make a difference if the pipe is running lower than the pump, otherwise no suction will be generated. What you are talking about is not really a siphon as such, as you are still pumping the water back to the sump, not relying on a suction action.
The only time suction would be generated, is if you turn your pump off, and the remaining water runs out of your solar system, creating a vacuum in your pipework. This will aid your pump on startup, but only until it equalises the pipework.

Yes, if your system is a closed loop that returns back to the sump, then the only work the pump is doing is to "circulate" the water through the piping and the solar collector; the "head" is 0 meters.

If you had an open loop where you dumped the water from someplace above the water level, then your "head" would be the vertical height difference between the outlet and the surface of the water.


It doesn't matter how deep the water is or how far down the pump is; it does matter how restrictive the pipe, elbows, fittings, and the solar collector are.

Great explanation and pic Dave. Well done

Sorry David-WI but i beg to differ-
The "head" is the difference between the top water line and the maximum output of the pump - my interpretation of what you have explained, is that no matter what height you are trying to raise, as long as it returns to the same water level you are working against "zero head" as you put it. To me, this basically means that a pump will pump as high as you want it, as long as it returns to its original source. Im not sure of the physics involved, as i realise that return suction will generate some sort of flow, but unless you cannot reach the required "head pressure", you arent going to pump anything.
I am guessing that the basis for this original question would be to aid in the selection of a certain pump- I would hope that the pump has not been downsized as a result of the above calculation. Your pump should sit appropriately in the curve supplied, which should in turn match with your flow expectancy (maxQ), in relation to your max head( as stated above).
The far right of your diagram shows that the fluid emitted to atmosphere is a measure of head. This is not the case. Any fluid that is open to the atmosphere will be at atmospheric pressure- velocity is a different story.(please insert boyles or benoullis laws here).

I will happily stand corrected.

regards,

Sam

That much is correct. LOL

so I can send my (factory stated 1.8m max head) pump up a 500m incline and back down with no worries? Why would we ever bother with booster systems if this is the case?

You have to allow for friction in the pipes as well.
How are you going to bleed the air out of the pipes?

Because, like you said... you don't understand the physics involved.

I believe riffraff is trying to understand this so how about you explain the "physics" instead of snobbing him off to not understanding David.

This forum is all about sharing so I hope you can respect this.

werdna, you are correct, you do have to account for frictional loss in your pipes, but that is a calculation of flow, not "head", as 4xjbh originally questioned, and yes, air locks would be a problem to be looked at.
Im sure David WI would love to baffle you with MS Paint pictures and patronising brainpower, but if the pump cannot push the water to the top of that garden shed as originally specified, or unless you are going to draw some sort of suction into the pipework every time the pump starts, the system will not work.
Please explain David, so all of us can understand, and please relate it to the practical workings of the scenario that 4xjbh originally enquired about.

There are all kinds of ways to fill the system.

You can fill the system before you raise it up to the roof. You can apply suction to the outlet using a wet/dry vacuum. You can fill the system with a garden hose. You can use a boost pump to get it full and replace it with the regular continuous duty pump.

But he didn't say his pump couldn't get the water up to the top of the shed; he asked if returning it to the tank in a closed loop would make it easier on the pump. The answer is "YES".

We run our pool water up to a solar collector on our garage roof, and it takes a little while for the pump to push the water up to the collector to fill it... but once it's full and the water starts flowing back down into the pool; the flow increases back to "normal". (Normal meaning "the same as it did with the collector on the ground" which is less than it flows without the solar collector in the circuit.)

I hope that's simple and practical enough for you; you said "I will happily stand corrected."

riffraff, i think how it works is similar to a siphon. The system will have to bled up first otherwise you would be correct. Gravity pulling the water down on the return side will create a low pressure which will then draw water up. As long as you have both sides of your pipe below the level of the water once it is bled up you wont have the problem of bleeding it up each time.

For more info, search for 'No Holes Overflow' or 'Water Bridge.' I was using one on my aquarium system which draws water over the side of the aquarium even though it was higher than the water level with out using a pump. The biggest problem is getting air in the system and having to rebleed it up.

I was planning to put a solenoid valve on both ends of the pipe run to keep the water in the line overnight and have them on the same timer as the low wattage pump. This is all theory for now as I wont get a chance this winter to get it operational.

Thank you for the feedback

Why bother with the solenoid?
Once the pump stops water isnt going to flow anyway