What Size Hydroponic Water Pump Do I Need?

By: Chris | Last Updated: May 18, 2021

Picking the right size hydroponic water pump or aerator isn’t rocket surgery. To select the best water pump for your hydroponic system you need to know a few things ahead of time.

First, what kind of system are you building?
Second, how large is the system?
Third, how high above the reservoir will the system be?

As long as you can answer those questions, I’ll help you answer the rest!

Already know what size pump you need? Check out the 5 Best Hydroponic Pumps & Aerators I use and recommend.

What Kind of System are You Building?

There are a lot of options when it comes to hydroponic systems. If you need help with that, check out this beginner’s guide to hydroponic systems. The table below will give you a general idea of the pumping power needed for your specific system.

Note: These values are gallons per hour (GPH) recommendations. I’ll help you calculate your actual pumping power (also called flow rate) a little further down.

Click on the links in the table to go directly to a specific section.

System Flow Rate (GPH) Total GPH
Nutrient Film Technique Volume x # of Chambers Flow Rate x Recirculation
Ebb & Flow Flood Volume x 201 Flow Rate x # of Flood Trays
Bato / Dutch Buckets 2GPH # of Bucket x 2GPH
Tower/Vertical Systems 2GPH # of Towers x 2GPH
Deep Water Culture Total System Volume (Gallons) Flow Rate = L/pm

1 The 20 multiple is based on a 3 minute fill time. Check out the Ebb & Flow Pump Sizing section for more information on calculating your own GPH Multiple.

Confusing? Don’t worry, I’m gonna walk through the calculations for each system type. Before we do that, let’s answer the last two questions.

How Large is Your System?

If you’re using a deep water culture system, it’s pretty easy to figure out how large the system is. For instance, if you’re using 5-gallon buckets each bucket is probably holding around 3 gallons of water.

To figure out the volume of an ebb & flow system, first plug the fill port so water doesn’t immediately start draining. Next, fill up a container with a known amount of water (5-gallon buckets work well here). Begin adding water to the flood tray until the water reaches the overflow port and begins draining back into the reservoir. Take note of how many gallons it took to reach that point. That is your flood volume.

Calculating the volume of an NFT system works similarly to an ebb & flow system. Plug the ends of one of your NFT channels, and begin adding water to the channel. Since NFT systems don’t use a lot of water, I like to use the marked 2-quart buckets you can get from a big box store.

Once the water reaches a depth of around ¼”, take note of how much water was added. This is the volume of a single channel. Multiply that volume by the number of channels in your system to get the total system volume.

Drip irrigation systems, aka Bato Buckets and Dutch Buckets, are pretty simple to calculate. Each bucket needs to receive approximately 2 gallons of water per hour. Multiply 2 by the total number of buckets to get the total flow rate needed.

Vertical and Tower systems are also easy to calculate volume. These systems need about 2 gallons of water per hour, per tower. Multiply the total number of towers by 2 to get your flow rate.

But wait, there’s more! There is one more question to answer before you’re ready to pick the perfect hydroponic water pump.

What’s Your Head Height?

Okay, not your actual head. Head height refers to how high your system is from the bottom of your nutrient reservoir. This is easy to measure.

To calculate head height, measure from the bottom of your nutrient reservoir (where your pump will be located) to the position where the pump hose will feed into your hydroponic system.

How to Measure Head Height

In NFT and ebb & flow systems this will normally be around 2 feet or less. Vertical systems will have a much higher head height since you’re pumping water to the top of a vertical grow chamber. Dutch bucket systems normally have a head height under 1ft, but there will be some additional reduction in flow because of how long the tubing is to reach multiple buckets.

Head height is very important because as the height increases, so does the weight of the water in the tubing. This water weight has to be pushed by the pump and creates pressure. As pressure increases, the flow rate (GPH) decreases.

Key Takeaway: Before buying a pump, make sure you can find its head height chart. This chart shows the flow rate of the pump at different heights. Check out the handy dandy chart below that shows head heights and flow rates for Hydrofarm Active Aqua pumps.

Active Aqua Hydroponic Water Pump Head Height Chart

If the chart looks like a bunch of squiggly garbage, don’t worry it’s easy to read. The vertical side is height in feet, and the horizontal section is flow-rate in gallons per hour. Each little square in the chart represents 2 feet in height and 200 gallons per hour in flow-rate.

So, now that you know that let’s look at a specific pump to better understand it’s flow-rate at different heights.

The Active Aqua 160GPH pump is represented by the tannish brown (I’m not a color expert) line. We see at a height of zero feet the pump can push 175 gallons of water per hour. At a height of 2 feet that rate is cut down to around 100 gallons per hour, and at a height of 4 feet the pump will only put out about 15-20 gallons of water per hour.

With that in mind, if you’re building a vertical hydroponic system that’s 6 feet tall, a 160GPH pump would not be able to push water high enough to provide any flow. Instead, you’d need to look at a 400GPH pump at the very least.

How to Accurately Size Your Hydroponic Water Pump

Great job! You’ve gathered all the information you need to accurately size a water pump for your hydroponic system. Below I’ll show you how I size pumps based on each system type.

Nutrient Film Technique (NFT) Water Pump Sizing

How much water does your NFT system hold? To figure this out, block both ends of 1 grow channel so water doesn’t escape. Using a measured container, like a 2-quart mixing container, begin to fill the chamber until the water reaches a depth of around ¼”. Take note of how much water it took to reach that depth. On average, a 5’ length of 4” PVC pipe will hold about a quarter of a gallon.

Why ¼” of water? In most NFT systems, you don’t want more than a quarter-inch of water flowing through the chamber.

Now that you know how much water it takes to fill a single chamber, multiply that by the number of chambers in your system.

0.25 gallon of water per chamber
4 chambers in the system

Minimum Pump Volume
Volume x Chamber
0.25 x 4 = 1 gallon

It’s important to recirculate the water flowing in the chamber to reduce bacterial growth. Recirculation also moves more nutrients through the system. I like to completely recirculate the water in the chamber every 3 minutes or so.

Recirculating Multiplier
1 Hour (60 Minutes) / Time to Recirculate (Minutes)
60 / 3 = 20

Calculating Total Pumping Volume
Minimum Pump Volume (in gallons) x Recirculating Multiplier
1 x 20 = 20GPH

Measure Head Height

Measure the vertical distance between the bottom of the nutrient reservoir and the grow channel water inlet. Once you know that height, reference the head height chart for your pump of choice to make sure the pump has enough flow rate at your head height to keep your channels flowing nicely.

The Active Aqua 160GPH pump has a flow rate of around 50GPH at a 2-foot head height when set to the low output setting. This is plenty of flow for a small system like the one I described in the example. You can dial in the flow rate and recirculation rate even more by adjusting the angle of the NFT channels.

Hydrofarm Active Aqua AAPW160, 2 Pack
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06/12/2021 04:32 pm GMT

Need more flow or faster recirculation? Increase the angle. If you need to slow down flow or recirculation, make the angle more gradual.

Ebb & Flow Water Pump Sizing

To size a pump for an ebb & flow system you’ll need to figure out how much water it takes to reach the overflow drain in the flood bed. This will give you the total volume of water needed in the flood bed.

To measure this, make sure your flood bed is filled with the media of your choice. I personally prefer hydroton expanded clay balls, but that choice is up to you. Once the flood bed is full of media, plug the fill port on the flood bed so water doesn’t immediately begin draining out.

Now it’s time to start adding water to the flood bed. Depending on the size of your system, the 2-quart buckets from big box stores (Lowes/Home Depot) work great for adding a known amount of water to the flood bed.

Fill the bed with water until it reaches the overflow drain, don’t forget to keep track of how much water you add. The amount of water it took to fill the bed to the drain port is the total volume of the bed.

If you’re filling multiple beds from a single reservoir, multiply the volume of one bed by the total number of beds.

Now that you know how much volume you need to pump, it’s time to figure out how quickly you want to fill the flood beds. I like to run my pumps for 30 minutes, 4 times per day.

Since the pump is only running for 30 minutes at a time, I like to fill the bed quickly so that the nutrient solution is cycled thoroughly. My goal is for the bed to start overflow draining within 3 minutes.

5-gallon flood volume
3 minutes to start overflowing

A 5 gallon per hour pump would fill this volume in one hour, but since we want to fill the volume in 3 minutes some simple math is required. To find the GPH multiple, divide 60 minutes by the number of minutes you want it to take to overflow the bed.

GPH Multiple
1hr (60 mins) / 3 minute fill time

Now that you know your gallons per hour multiple, multiply that by the volume of water (in gallons) to get the minimum pumping power you’ll need to efficiently fill the flood table.

Minimum Pump Volume
GPH Multiple (20) x volume (5)

In this example, a 100GPH flow rate will fill a 5-gallon flood bed in 3minutes.

Don’t Forget About Head Height!!!

Make sure you check out the head height chart for the pump you’re thinking about buying to make sure it has enough flow rate to the bed.

Looking at the chart above, the Active Aqua 160GPH pump has a flow rate of 100GPH at a height of 2 feet. If your flood bed is within 2 feet of the bottom of the nutrient reservoir, this pump will work perfectly. 

Ebb & Flow Flood Bed Volume

I use an Active Aqua 160GPH pump to flood this table. It begins overflowing/recirculating within 3 minutes.

Bato Bucket / Dutch Bucket Water Pump Sizing

No matter what you call them, bato bucket hydroponic systems work sort of like a drip irrigation system. They’re not technically drip systems because most of these setups don’t actually use drippers or emitters.

Each bato bucket in your hydroponic system needs to get about 2 gallons of water per hour. If you’re like most people, you probably have a ½” main tube with ¼” “drip” lines running to your plants. The drip lines will create some pressure in the system, and flow rate will decrease.

Minimum Pump Volume
# of Buckets x 2 (GPH)

Measure the head height from the pump to the top of the buckets and make sure to take that drop in flow rate into account when selecting a pump. A 160GPH pump should work fine for 4 or 5 bato buckets. A 250GPH hydroponic water pump can easily handle 10 buckets.

How to Size Your Hydroponic Aerator

Aerators play a major role in keeping hydroponic systems healthy. They keep reservoirs oxygenated, and their ability to break up the surface of the water also helps keep algae growth at bay.

Aerators are sized in liters per minute (L/pm). An output of .5-1.0 liters per minute, per gallon of water in the nutrient reservoir is recommended for aerators used to oxygenate nutrient reservoirs.

Simply put, if you want to aerate a 20-gallon nutrient reservoir select an aerator with an output somewhere between 10-20L/pm.

Active Aqua AAPA15L, 6W, 15 L/min Air Pump
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06/12/2021 05:32 pm GMT

Deep Water Culture Aerator Sizing

In most applications, deep water culture (DWC) systems use aerators instead of hydroponic water pumps. You don’t need to pump water to the root systems since the roots are growing down into the nutrient reservoir already.

If your deep water culture system used 5-gallon buckets, remember that each bucket probably only has 3-4 gallons of water in it.

6 5-gallon buckets with 3 gallons of water per bucket.

Convert System Volume to L/pm
Total Container Volume (Gallons) = L/pm
3 gallons = 3L/pm

Calculate Total System Volume
Number of Containers x L/pm
6 containers x 3L/pm = 18L/pm

In this example, you would want an aerator that could output at least 18L/pm.

Buy a larger aerator than you need. You can adjust the output either on the aerator itself or by adding small gate valves to the tubing.

The surface of the water should be bubbling, but not so much that it splashes water out of the container if the lid is off.

Chris Cook started Happy Hydro Farm to share his passion for hydroponic gardening! Growing your own food is incredibly rewarding both physically and mentally. His mantra - "Take excellent care of your plants, and your plants will take excellent care of you."