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 that need to be moved per hour
- head height
Let’s take a look at each variable, then how to combine them in a way that will tell you what size of pump you need.
(If you start feeling overwhelmed at any point during this post, just pick up a phone and call one of our super-friendly team members at our office: 307-766-6538. Rikki and Amy have got your back!)
How many 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 that favor the metric system will use liters per hour. (You can use the same equations, just remember that if you change one unit you have to change all of them.)
Figuring out GPH is easy.
In hydroponics, you want to run two gallons of water through each tower every two hours. This means that the number of gallons is essentially the number of towers, times 2, then divided by 2… or just the number of towers.
Of course, you’ll also have a bit of extra water in your sump- a good rule is to add fifty gallons for the sump. So, you end up with a gallons per hour (GPH) for hydroponics equation like this:
In aquaponics, you’ll want to run seven gallons of water through each tower every two hours.
Since you’ve got the fish tanks as well, you also need to factor in the fish tank gallons. You’ll also be turning over the fish water every two hours, so the gallons per hour for aquaponics equation looks like this:
So, let’s say we have a 100 tower 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. Then we’ll add on 50 gallons for a sump tank.
That means we’ll need a minimum of a 100 GPH pump.
Boom. One factor done. Keep your GPH number on hand; next we’re talking about head height.
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.
To compensate for the height, we use a measurement called head height.
What is Head Height? *
Head height is the distance between the top of your grow bed (or ZipGrow tower) and the top of the water in your tank.
You won’t even need to do a calculation for this. Just measure the length between your pump and the top of your irrigation (which is probably the drip lines above your towers.)
For example, If you have a pump at the bottom of your sump, which is 4 feet below ground level, and you’re irrigating your towers 5.5 feet above ground, your head height is 9.5 feet. Simple, right?
Combining GPH and Head Height *
See the chart above? That’s you’re cheat sheet, and most pumps come with a chart like this that matches their strength specifically. (Make sure you’re using the right chart for your type of pump. Inline pumps and submersible pumps function completely differently.) Using the GPH you calculated and your head height, find the pump that matches your needs.
Usually pump efficiency at different head heights is almost never a linear relationship (again, check out the example on our pumps).
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 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).
Pumps for Aquaponics or Hydroponics *
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