nft pump choice

[sanchini]

I'm trying to grow vertically using a low power setup, my current design has to move the water up to around 5-6'. I'm planning on using NT rather than the planned ebb & flow, then using a number of tiers to fill vertical space with greenery. I'm struggling a bit with pump choice.

Is there a simple way of estimating flow with different head lengths? Does anyone have experience of a very low power pump that has a suitable head rating? Efficiency is important.

Currently there's no FT, although the aim is to introduce aquaponics to it. I can get away with far less flow to experiment with the rig without fish.

Thanks.

[foodchain]

How many GPH are you looking for?
What kind of wattage?
What inlet/oulet sizes would you prefer?
Do you prefer submerged or external?

[sanchini]

My thoughts are 15 gph, down 4 1.5 meter long gullys. I have no specific preference on type but thought submerged would stay cooler. Wattage is as low as possible, the first build will probably be grid powered but ideally a 12 volt dc pump is the goal, lowest consumption possible. For now a stable pump to experiment with is fine. Have given no thought to inlet size etc, would appreciate some input if it makes a big difference.

[foodchain]

15 GPH is not very much. Do you plan to have this run countinous then? Sorry I am a little confused. I suppose if your not doing the ebb/flow that would be okay. Are you dividing it between 4 different troughs, or cascading one to the other?

[sanchini]

I'm thinking 4 trough sections one after the other, the pump only supplies the first, it cascades through each in turn down to the reservoir. The pump will be on continuously.

[bsfman]

I'm trying to grow vertically using a low power setup, my current design has to move the water up to around 5-6'

Most pumps you see in shops or advertized online show max head and flow rates at different heights. If you interpolate, you can guess close to what the flow rate would be at your desired height. You can always throttle back a "too-powerful" pump by restricting the output with a valve or diverting part of the flow back to the fishtank. Better to have a pump rated for more than you think you will need than one rated "just enough".

[sanchini]

thanks, all very helpful, the first design is underway, will start buildings frames within the week. Will get photos up soon.

[foodchain]

Be carefull. Simply reducing flow by restriction will increase stress on a pump. A process similar to dead heading. Instead put a diverter or Y fitting in the outgoing flow. Add a valve for adjustment on the line to the beds. The other line returns to FT to recirculate, and aeriate the water. When valve is completely closed, the water simply circulates in a small loop. When open, very little water by comparison comes out the disconnected end. Use extra pipe to route your non FT end back towards the tank to increase hydrostatic pressure/resistance on it, but also to have better control of extra water. No sense having it fly loose and get water on everything. PVC 90's and 45's work good for this.

[keith_r]

+1 foodchain..
and you should pre-filter your water before it goes to the nft channels/pipes or you'll have problems

[bsfman]

Be carefull. Simply reducing flow by restriction will increase stress on a pump.

I've always heard that restricting the input to a pump is hard on the pump, but not so restricting the output. Not trying to be argumentative, foodchain, just interested in learning what difference there would be in using a valve to restrict pump output by say 50 percent or using the same pump at some elevated level of head where it is pumping at 50% capacity? Whether it's mechanical restriction or gravity causing the rate of flow to change seems immaterial to the effect on the pump.