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The Hydroponics PumpThere are three flavors of Hydroponics pump available; submersible, non-submersible and what I term, semi-submersible. A submersible sits and pumps completely submerged in the nutrient solution, a non-submersible is an external unit outside of the nutrient solution and a semi-submersible sits in the solution to pump but the top of the pump must remain dry. I do not personally think very much of this kind of pump. I purchased one with my first pre-made hydroponics system and within a half hour it fell over into the water and destroyed itself. It was a miracle I wasn't electrocuted... My personal preference for a hydroponics pump is a fully submersible type. Here is a picture of the fully submersible pump that I use:
Let's assume for a moment that you wish to purchase a hydroponics pump but don't know how to procede...The first thing you need to determine is how much nutrient solution you wish to pump. To do this you need to figure out how much nutrient solution will be in your growing container that is filled with growing medium. So... Let's say hypothetically that your growing container is 20 inches long by 16 inches wide by 8 inches high. The height is measured from the bottom of the container to the top of the growing medium which will be about even with the middle of the drain outlet in an ebb and flow system. 20 x 16 x 8 = 2560 cubic inches Divide this by 1728 (12 x 12 x12) to convert to cubic feet. 2560 / 1728 = 1.48 cubic feet Growing medium takes up volume but different types of medium take up different volumes so as a rule of thumb, rockwool takes up 20% of the volume of a container, clay pellets, 30% and pea stone, 80%. So if we use pea stone, which is a good choice for a large container due to its density because it means less nutrient solution to deal with, we would take the 1.48 cubic feet and mutiply it by 20%. Since it takes 80% of volume the remainder is water which is 20%. 1.48 x 20% = 1.48 x .2 = around .3 cubic feet. Since 7.5 gallons of water are in 1 cubic foot, 7.5 x .3 = 2.25 This means that our container filled with 8 inches of pea stone will hold 2.25 gallons of water so we want to choose a hydroponics pump that will pump 2.25 gallons of water into the growing container in about 12 minutes. This is a general estimation only; you want nutrient solution into your growing medium quickly but not quickly enough to disturb plant roots. We need 2.25 gallons pumped in 1/5 of an hour so 2.25 x 5 = 11.25 gallons per hour or GPH. Since most pumps are rated above 100 GPH you would think you're covered, right? Wrong! We have to consider 'PSI' and 'Head'. PSI refers to the power of the pump and head is the distance in feet from the pump to the input to the growing container. To figure this out, click
how to rate a pumps capacity
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