Sizing a Pump for Aquaponics or Hydroponics
Variables For Calculating Pump Size
Figuring out the correct size of pump for you aquaponics or hydroponics system is something beginner growers run into when starting out. In order to determine the best pump for your system, you’ll need to analyze a few variables.
Gallons Per Hour
Pumps will almost always have a Gallons Per Hour (GPH) rating that tells you how many gallons of water that pump will move every single hour. Obviously, places who favor the metric system (which is really most places around the world) will use liters per hour.
Pump Height Efficiency
Because almost all aquaponic or hydroponic growers need to move water upwards, you’ll need to also understand how efficient your pump is a different heights. Even if you’re still using a traditional horizontal grow bed model or NFT, as opposed to a high density, productive powerhouse like ZipGrow Towers, you’ll still need to move water vertically from your fish tank to your beds or troughs.
How Much Water Do You Need To Move?
Before we can delve too deeply into pump height and efficiency, it’s crucial to understand how often you’ll need to turn over (fully cycle) the system water.
We recommend that hobby or small commercial aquaponic or hydroponic growers turn over their system volume at least once every two hours. While there is some flexibility here, a good place to start when you’re calculating the size of pump you need for your system.
Hobbyist Aquaponic Scenario
So, let’s say we have a 100 gallon system. Thinking about our minimum recommended amount of water we should be moving, we’ll need to move 50 gallons per hour in order to turn our entire system volume over at least once every two hours.
That means we’ll need a minimum of a 50 GPH pump.
BUT WAIT. Remember, almost every person reading this post will be moving their water up in some form or another. This includes people using traditional IBC systems, who need to move their water at least two feet of head height.
What is Head Height?
The distance between the top of your grow bed (or ZipGrow Tower) and the top of the water in your tank.
Now, you’ll need to look further into what pump your using and find the efficiency and head height info usually posted on the side of the box(see photo on left), or contact the manufacturer directly.
Usually pump efficiency at different head heights is almost never a linear relationship (again, check out the example on our pumps).
Now, back to our hypothetical example. If we look at the chart on the whiteboard (see video), we’ll then figure out that when we need to move the water two feet vertically, we’ll need a pump with a head height of 30 PGH. Any pump capable of pushing 30 GPH (or more) at two feet will work great for our application.
Other Important Considerations
When choosing a pump, remember that our recommendation of turning over your entire system volume at least once per two hours is a recommendation. If you shoot a little long, or fall a little short of this recommendation, everything will probably be just fine.
Just remember that every aquaponics or hydroponics system out there varies considerably. Whether the it’s the plumbing, system design, grow media, etc., every system is different and required GPH can vary because of it.
The important thing to remember is that you are exchanging your water fast enough to maintain a good level of dissolved oxygen in your system. Try to avoid those lethal anaerobic zones in grow beds or towers.
When researching pump efficiency and GPH and various head heights for your own application, remember that you’ll be moving water through what could be quite a long length of hose.
That said, the further your system volume travels, the lower your pump’s efficiency will be, and that could mean a decreased GPH or overall system performance.
While it’s possible to do the efficiency calculations here, it’s much more simple just to eyeball it and calculate anywhere from a 15% to 30% loss of efficiency (this of course depends on your plumbing and system design).
Questions? Post them to the comments below and be sure to share this content if you’ve found it helpful!