pump question and DWC
 

Hi, I want to build a sort of recycling deep water culture system, I want to pump water into the bottom of my buckets and at the top a overflow that drains back into the reservoir. Is it OK to use a water pump in this fashion? I mean would the pressure of the water in the buckets damage the water pump?

If using standard water fountain pumps or pumps from a hydroponic store you should not have any problems. If the presser builds they just wont be able to pump as much as fast. These type of water pumps use magnetism to spin a shaft, and because they are submersible there are no moving parts between the shaft and coil. The bearings are replaced by water. You don't want them to run dry or they can burn out.

If the water is pumped into the buckets from the top of the buckets above the overflow, there wont be any back presser (from the water in the buckets anyway). And you wont have any issues of leaking through the water inlet hole seal either. If you want the water to mix better than just dripping in from the top, you can extend the water inlet tube down below the water level. As long as it's coming from over the top and down into the bucket it wont need to be holding back the water in the bucket as it pumps in (causing back presser).

Keep in mind if extending the inlet tube down below the water level, when the pump is shut off it will Siphon back into the reservoir to the point of the end of the inlet tube. You can drill a small hole in the extended inlet tube at your overflow water level, this will stop the siphoning action at that point.

(note: just to be clear, the addition of a water pump in this type of system does not replace the air pump. You will still need the air pump running 24-7 in the growing buckets.)

Excellent thanks! I am growing outdoors and the problem is using standard air pumps outside in possible rain, I have brought a fairly powerful submersible air pump that I am going to use in my reservoir and the pump itself has a attachment that sucks air through a tube and mixes it with the water (multi 4000 http://www.sicce.com/foto/prodotti_allegati_74.pdf ), I will try this out and see if it going to produce enough oxygen. Thanks again.