Hydroponic Pump SelectionAs an example, suppose we have a system that needs a pump capable of delivering 11.25 GPH or gallons per hour. Now suppose the length of the tube from the pump to the growing container inlet is 3 feet. As we are browsing online we find a pump rated at: 120 GPH @ 1 foot head with 2 PSI. Would this pump serve our needs? It would seem so on the surface so let's make sure. A rough rule of thumb is to double the PSI to determine the lenght of 'head' at which a pump will pump 0 GPH. This pump is rated at 2 PSI at 1 foot head so at 4 feet head it will not work. We have 3 feet head. 120 GPH at 1 foot head leaves another 3 feet for GPH to drop off to nothing. So, 120 / 3 = 40 meaning a 40 GPH drop for every foot of head from 2 feet onward. So with a 1 foot head this pump will pump 120 GPH, with a 2 foot head; 80 GPH, 3 foot, 40 GPH and 4 foot; 0 GPH. Since we have a 3 foot head we can expect a 40 GPH capacity from this hydroponic pump. If we subtract another 5 to 10 GPH for growing medium resistance and tube size, we can realistically only expect 30 to 35 GPH. Since we need 12 GPH we are pretty much covered... I hope you find this method useful we actually do go out and select a pump. If you do, I would love to hear about it...
|
