High Pressure Aeroponics (HPA) misting frequency


I am currently growing in a high pressure aeroponics system. I’ve have grown tomatoes and lettuce in the past with great success. I think managing the nutrient side of things is one of the easier aspects of growing with aeroponics, however what has always baffled me is the misting in the root chamber. I’m confident in the mist being produced is true high pressure aero mist based on the nozzles and the 90-100 PSI pressure. I can’t say that I’ve measured to the water dropplets to ensure that they are 50 microns… but it’s super fine like an aerosol can spray. However, I really don’t know what the misting duration or frequency should be. Currently it’s misting for 2.5 seconds every six minutes. The plants and roots look healthy, however I can’t help but wonder if they’re getting the optimal amount of mist. I have a plant camera that takes a picture every hour and have been thinking about setting up a root camera to help with checking on the health of the plants. I realized that the misting frequency/duration are also closely related the the specifics of the misting chamber itself (size & number of nozzles & nozzle type). If anyone has any suggestions or can send me in the right direction I would be happy to report back the results to all fellow nerd farmers.

Aeroponic System Categorization (flex/vertical/horizontal trays)

I am documenting myself at the moment, but there seems there is no specific cycle for all plants. Must of the information in aeroponics I got where from weed planters like http://420dotcom.com/diy-aeroponics-new-high-pressure-aeroponics-diy-plans.html, where sets the cycle 30 sec. on and 2 min off. Yet there are papers like http://www.academicjournals.org/article/article1379513341_Mbiyu%20et%20al.pdf, where the cucle is set5 min on, 15 min off.


I have no data backing this idea at all- as I’m in the process of making a tower to grow veggies outdoors.

But it dawned on me that if there’s not enough water, then there would not be any run off at all. Which makes sense. Which suggests that a good measure of just enough would be barely any run off.

That’s assuming that the roots are a good temperature, of course. As I see that as a second purpose of watering…

Perhaps that’s something that can be experimented. I need to keep that in mind for this summer.


I think the frequency and during will ultimately be determined based on visual feedback. If the roots receive to much mist then large water droplets will smother the roots and they won’t be able to take up oxygen as easily, I do not aerate the reservoir. Too little mist and the roots could dry out and will not be able to pickup as much nutrients (General Hydroponics Flora series).

During a mist cycle the majority of the mist doesn’t even touch the roots. I was initially concerned the 4 nozzles for a 40"x19"x17"deep misting chamber wouldn’t be enough. However, I’ve had no issues… not even a clogged nozzle. I am thinking about off setting them from their vertical position with the hope that a vortex would be created that helps swirl the mist around and penetrate the dangling roots. I am going to physically hang the roots on a root ladder in the chamber to prevent a large glob of roots on floor of the chamber… to help the mist find the roots without soaking them.

Again, I think it’s a question of looking at the roots. I am absolutely confident that aeroponics is the ultimate method for growing the most, with the least resources in the shortest amount of time. We just need to have more information on this growing method.


The whole misting cycle and how many nozzles question is one big reason why I’m here and posting.

Perhaps there’s some good info on one of the, well… growing groups…

But this being an academic endeavor, it’s a good place for data and ideas to be shared. So I see this place as where the “more information” will end up being.

For my plan, I can’t thank you enough, adam, for posting the information you have. Between the 4 nozzles for the good sized chamber to the different cycles- that’s really awesome for me. Now I know that I can use probably just 2 for my experiment- one at the top pointing down, and one at the bottom pointing up.

The experiment that I’m running this summer is the low pressure (usually the head pressure of a tank pump) vs. high pressure (80psi). The idea is to compare growth as well as cycle required for the low pressure system. The set up will be 2 5 foot sections of 4" PVC using 1.5" elbows as the growing locations- and both systems will use the same water source.

The reason that’s what I want to experiment- I see 3 types of “aeroponic” towers- one drip one, low pressure, and high pressure. The drip system runs 15 min on, 15 min off- so during a day, that’s 12 hours of pumping. The high pressure I was targeting was 3 seconds on, 3 min off- or about 15 min a day. So if one was to develop a stand alone system using a small battery and solar collector- the high pressure system is very feasible. The low pressure system is slightly less expensive to put together, and if it can be anywhere near as good- then it would be a less expensive system in isolated areas.

I know the high pressure is the “true” system that NASA developed- but reading an SAE paper kind of implied that the lack of gravity had a lot to do with the small droplet size requirement- small enough to not get into droplets that cover the root- as it can’t drain off. but big enough to hit the root systems. It’s SAE 2000-01-2507 if you are interested.


I really think you want something wider than 4" PVC for the misting area, especially for HPA. Having plenty of space for the mist will minimize the amount of mist that will come in contact with the walls. Keep in mind that as soon as the mist hits the walls it will stick and then just drip down the sides. I would also recommend that you try to always mist upwards, this way gravity is working with you and the water droplets will get more “air time”.

Personally I wouldn’t even bother with the low pressure aeroponics test… but that’s just my 2 cents.


On and off cycle timers aren’t as important as coverage and absorption. One of the reason high pressure systems are preferred is its ability to deliver small droplets (atomized droplets increase absorption) deep into the root mass. The healthier your roots are, the harder it is to reach the inner layers with nutrient solution. The more root surface you spray, the faster it absorbs. On the other hand, the wetter your roots stay, the less effective they are at taking in oxygen and the slower they absorb nutrients.

I think the goal is really to mist the roots just enough so the individual droplets stick to the roots. The time between sprays should probably be a little shorter than whatever it takes for the plant to absorb the droplets or have them evaporate. This time changes with things like ambient temperature, nutrient temperature, nutrient mix, air flow, root surface area and plant type.

Think of your roots like tourists at a theme park standing under one of those “cool off” tents. If you spray them too much, they get wet and angry.

Hopefully that helps.


Thank you Bkirkland for responding. I absolutely agree that it’s more of a feel than a time/frequency matter. Unfortunately it’s pretty awkward to access the root chamber given the size of the pants and my chamber design. My next version will have access for observation and root manipulation. Another Idea I have been mulling over is switching to a venturi style nozzle which would be capable of producing the droplet size but would also have the force of the air which could help with root penetration.

HPA… The Way to Grow


Hi, I hope you don’t mind if I add a more general aeroponics question to this thread.
Has anybody built the PFC using an aeroponic system instead of the hydroponic approach? If yes, what were the main hardware and software changes you had to make?


Hey fellas I ran across your post because I was researching with the difference between high pressure mist, forgers, even nebulizer. I’m in a first build and have a box several feet wide and long. Plate atop with holes 3 1/2 round for the cups. In the end I think high pressure is the way to go but read articles about the misters being to powerful. My build is three feet tall. Leaving that much of hang for the roots. Planned on installing misters six inches from the floor. Which would be 2 1/2 feet of root hang. First question, what metric do I use to determine what the right nozzles are supposed to go in a 6 ft long, 6 foot wide, 3 ft tall box. Just keep adding until it looks right? Is there a meter for that? Second, what adjustments should I be making to my dementions etc? I guess as a thought. I read tech articles, even some forms that referred to a mass of what we see as soakaponics. Lol. So I’m thinking of inserting a number of tiny holes in the top of my box spread equally across with valves. When my fan in the box triggers, (to vacuume out the whole box for the above said 30 or 5 min cycles) instead of the air coming from the other side with, say, another fan, it is coming from above and traveling through the root system before leaving the one channel. What do you think? P.p.s. Anyone know what my math should be for this vacuume process? Your post above are among the best I’ve seen. Thanks.


Hi Adam
I would recommend root chamber no less than 15"-16 deep for high pressure aero. As for mist timing,a lot depends on the mist quality (droplet size range), nozzle flowrate, coverage and level of control you have…
In an ideal system, you would set the misting duation basd on flowrate and chamber volume. For early growth, the misting duration would provide 0.02ml -0.04ml per gallon of chamber volume. For later growth, 0.06ml per gallon.
The interval between mistings is adjusted to provide the target daily throughput, which will be somewhat dependant on environment variables (light,heat etc). As an example, a 26 gallon chamber with one 1gph nozzle would need a 0.5- 1 second misting duration in early growth and upto 1.5 seconds for later growth. The interval between mistings for early growth would be 35-70 seconds (dependant on the misting duration setting) with a target daily throughput of 1.3 litres. For later growth, the interval would be around 50 seconds with a target daily throughput of 2.65L. The name of the game is to inject mist little and often to maintain an optimal aeroponic environment.
Most aeroponic systems have flowrate, coverage and/or control limitations which provides a defined wet/dry cycle rather than a constant mist environment.


MVP - Product Design

Choosing the correct nozzles involves matching the mist pattern to the chamber and/or planting layout. Nozzles come in a wide range of types, full cone, hollow cone, flat fan etc. To make things more interesting, there are various.cone angles and short and long throw. Consider which nozzle pattern/type provides full and even mist coverage with the fewest number of nozzles (as this affects the system flowrate). For example,.narrow cone long throw nozzles are best suited to long narrow chambers with rows of planting sites. The mist is directed horizontally into the space between the two rows, This will generate two walls of roots running the length of the chamber with an open corridor of space allowing mist distribution. Be aware that roots can and will thwart even the best laid plans as they can sense where the nozzles are located and will try to grow towards them., Roots can grow horizontally into open space ( defying gravity),they can climb UP a sheer chamber wall and even attach themselves to the slick underside of a chamber lid to get closer to a nozzle. Making the nozzle locations adjustable is a good idea as is having nozzles that are accessible from OUTSIDE the chamber for easier maintenance.


Hey guys, great projects here!

We offer a variety of misting and fogging nozzles to help you achieve your mission.

Check out https://www.cool-off.com/accessories/misting-nozzles for our full line of nozzles and feel free to reach out with any questions about our products.




@Cool-Off I’ve been wondering for a while about pumps to drive a small high pressure misting system. I just checked your site and saw some kits with a pump, RO filter, tubing, connectors, etc. that sell for over $1000, but it seems like those are designed for large scale stuff like misting a patio. Do you have any experience with smaller, less expensive pumps that might be suitable for a small DIY aeroponics setup? If so, I’m curious how loud they are, how much space they take up, what the power requirements are, etc.


@wsnook Here’s a link to the one I bought and am using. https://www.aliexpress.com/item/2016-New-12V-DC-100PSI-4L-Min-Diaphragm-Water-Self-Priming-Pump-High-Pressure-For-Car/32613383652.html?spm=2114.13010608.0.0.yOS6bI

I bought a 300ZAR (~20USD) patio misting kit(designed to connect to tap water supply) and I am using that for my system. Alternately, these are identical to the misters that came in my kit.

35W power consumption, I’m using it with a computer PSU. I doubt I could sleep in the same room with its intermittent noise, but it’s around as loud as a running microwave.

Here’s a picture of my setup. I’m using a 1.5s on, 5 min off cycle


Reverse osmosis booster pumps are very quiet running (almost silent) and will give you a little more psi. My experience of the brass patio misting nozzles with 10-24 threads is they are very prone to partial clogging even when you use good filtration, be sure to check them every day :wink: