Choosing the proper hydroponic pump can be an easy mission. In a nutshell, we need enough power to pump the water through the main water line and into the smaller feeder lines with enough psi to make them drip.
For most hobby growers, submersible and sump pumps are plenty of juice. For larger operations, strong, costlier inline pumps can be used.
Calculate Pump Size
To calculate the pump required, we can get the gph(gallons per hour) rating at the head height we will use. The pumps come with this information. An example is shown below.
Once we have a our gallon per hour rating, we need to calculate how much we use per hour. We do this by calculating our dripper rating and multiply that number by our amount of drippers. For example, if we have 250 drippers delivering 1/2 gal per hour each, we need 125 gallons per hour of liquid water and/or fertilizer each hour.
Although the previous numbers are very useful, it still does not tell us our exact pump size because the drippers have a psi rating. For example, a dripper may require a minimum of 7 psi to drip liquid.
In addition to dripper psi, a 15% inefficiency is a good allowance for the pump itself.
With all the previous info, we finally need adequate psi. We can easily measure this with an inline pressure gauge. Two key points to keep in mind is that our tubing, fittings and drippers will all have min and max psi ratings for which we should never rise above.
With previous said, a weak pump will not deliver to all the system, or parts of the system(particularly at the far end). A strong pump can always be controlled with a bypass valve inserted directly after the pump itself. In addition, a pressure control valve(common size 25 psi) can be inserted before any lines to ensure psi is stabilized.
When growers begin to use pumps, they often start with a smaller submersible pump and work their way up. In this case, starting with a 500-1000 gph submersible is easily adapted with a bypass valve to handle tiny and gardens and even mid-size ones requiring 100 drippers with 6 ft head(height of header line above the pump).
As we expand, we will just scale up. Here is where sump pumps come into play. Not only will they deliver for volume, they will have more horsepower.