Eliminating Clogging in HPA, and "stream misters"?


#1

Hey everyone, I’ve really enjoyed some of the past discussions on Aeroponics on the site, and wanted to get a new one going. I’ve recently been testing these brass nozzles, and have had to replace nearly all of them after a few days of operation.


These, and many other off-the-shelf misters were obviously designed for misting low ppm water, and not nutrient solutions.

So I wanted to know: What are the best misters you know of that reduce clogging? And, do you know of a solution that eliminates the issue all together?

And on a side note, I recall reading this interesting bit on a New Yorker article interviewing Ed Hardwood, the founder of Aerofarms, on his claim of solving this issue with “more of a stream than a spray”, what do you guys make of this?
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#2

My advice is to read all of atom’s old posts and replies again. Also, you could search old forum posts for “nozzle”.

I don’t have any aero growing experience, but I’ve followed the discussion here closely. There seems to be a theme where people hear about some way of using cheap parts to build an aero system, they really want it to work, they try it for a while, and then it doesn’t work. Atom has explained a lot about designs incorporating hard-learned lessons on how to make aero work well for growing.

[edit: Also, be careful with using brass parts for growing food unless you know they’re made with a lead-free alloy. Lots of brass has lead in it, and the lead can easily leach out.]


#3

Thanks for the advice, wsnook!

I love Atom’s posts, his insights have informed a lot of my design decisions thus far (drain to waste, solenoid equipped accumulator and more), and you’re right I should go back and read through them again, see if there is something there I missed.

I know exactly what you mean, I started on my system half a year back, with the hopes of using cheap parts everywhere I could only to have them not work in growing. Since then, I’ve upgraded nearly all of them but I’m still left with bad misters.

I guess to be more clear, what I am really looking for is a link to buy a good set of misters that don’t clog, and whether that means I will need to use compressed air. Maybe @Atom already left a good answer for this in past replies, so I will be checking.


#4

If you want specific advice on nozzles, it will probably help to give a detailed description of your system. Dimensions for the root chamber? How many plants? What’s the spacing like? Pictures? What kind of pipe are you using for the pressure lines? How long is it? Where are your solenoids? What pressure do you run at? How do you maintain that? How do you control the timing to switch the solenoids? What nutrients are you using? How hard is your water? Are you filtering it? If so, how? What are you doing to adjust the pH? What EC do you mix your solution to? etc.


#5

My system takes water from the mains (~100 psi), through a 2 stage R/O

…Through a dosatron (controlled via solenoid)

…into a 2 gallon accumulator tank

…and according to arduino code, the solution then gets sent to the misters via 1 solenoid

The three misters are threaded into a 1/2 inch pvc pipe.

The nutrients that the dosatron mixes are a concentrated water soluble organic mix from Dutch Nutrient, tuned to 4571 ppm, 2 ph, which with a 3% setting on the dosatron, become a 6.6 ph and 480 ppm solution for growing kale.

The Kale seeds I grow are spaced almost like micro greens, and sit on a coco mat (intended for micro greens), held up by metal rods, the roots poke through super fast and remain suspended in the mist until harvest. So you could say I took a lot of inspiration from AeroFarms (minus the cloth).

The root chamber is a 9 inch deep, 10x20 inch stainless steel tank, with a hole at the bottom (for drain to waste operation).

Hope that’s enough information, let me know if you have any other questions, and any nozzle suggestion would be amazing. Last nozzles I successfully grew kale with never clogged but had giant droplets.


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#6

Nice! Functionality aside, I like how your build looks. The pictures are helpful.

Keeping in mind that I don’t actually know what I’m talking about when it comes to aero, here are some things that jump out at me based on what I recall of atom’s posts and my general vague knowledge of plumbing:

  1. You’ve got a long-ish looking flexible hose with a couple sharp bends in it going from the dosatron to all the bits by the accumulator. I wonder what pressure you’re actually getting coming out of the solenoid. It might be less than you think. Maybe a lot less. [edit: on second thought, your accumulator should take care of any drop from the flexible hose. If there’s a pressure drop, it would be between the accumulator and the nozzles.] Atom talks about using booster pumps, but it looks like you’re relying on mains pressure.

  2. Your PVC manifold after the solenoid looks like it holds a fair sized volume of water. I’d guess you might have a long-ish period (relative to the time at your highest pressure) at the start and end of a cycle where the pressure is ramping up and ramping down. That might give you lots of drops and dribbles around the nozzles. One of atom’s pictures shows a stainless nozzle screwed into a short manifold with solenoids for air and nutrients. Atom recommended once that it’s good to peek inside the chamber, or use a video camera, to watch the misting pattern and time how long you’re actually misting.

  3. Your nozzles are flat and pointed straight up. It looks like they have little puddles of nutrient on top of them. As the puddle on top of a nozzle evaporates, it makes sense that nutrients would accumulate and clog the orifice. If you pointed the nozzles at more of an angle, or picked nozzles with a more rounded or pointed shape, maybe the nutrients would drain better at the end of your cycle.

  4. Maybe your nutrients could be more diluted. In this post, Aeroponic System Categorization (flex/vertical/horizontal trays), atom mentioned “100-250ppm (EC 0.2- 0.5)” for lettuce.

Sorry that I don’t know anything useful about what nozzles might work better or where to get them. This comment has some keywords you could try searching for: High Pressure Aeroponics (HPA) misting frequency. [edit: You could also try looking for university agricultural extension program websites that give advice on nozzles for spraying pesticide (look for stuff like, “don’t use this kind… because it will make a mist that floats in the air”–for aero, those are the ones you want).]


#7

Thank you so much for your write up, all of these points should prove to be really useful for me.

  1. Your edit is correct but your first point still stands because I will be experiencing pressure drops from both the R/O filters and the dosatron which are both in place before the accumulator. I should perhaps still consider a booster pump.

  2. This is something I also hadn’t considered much, but it obliviously affects mist quality greatly. I might not get to solving this soon but seeing that picture really shows me what and ideal solenoid placement looks like and what I should aim for in V2.

  3. Again, I’m not considering the details enough, so this is another one I will have to keep in mind.

  4. That comment actually influenced my original blend. Kale needs a bit more nutrients than lettuce, but you are right, 480 still seems like too much, especially for early growth.This is an easy fix, perhaps I will take it down to 200 or so.

As for the nozzles, that should help me and I think I might be closing in on some soon. They seem to be tricky to buy online, but I should be able to find something.


#8

Hi Tino
I can see you put a lot of thought into your system :wink: I use mains water (75psi) for a big aerocloner No RO or dosatron needed for the cloner so its just the accumulator, 2 solenoids, pressure switch and a cycle timer.My mains water is always cold (~50F) so the accumulator allows it the time needed to rise to room temperature before going to the cloner :wink: The pressure switch controls the inflow solenoid to the accumulator. I dont recommend hooking the mains water directly to the misting solenoid as, apart from the water being too cold, it will usually result in water hammer issues.
The ideal nutrient strength will depend on the variables and growth stage, the easiest method to to check the run off ppm and compare it to your input ppm (480ppm). It can be tricky to acquire enough run off to measure with hpa. The best solution i could come up with involves a cheap HM digital DM1 (twin sensor) tds meter and a trap or simple u-bend in the chamber drain which provides a self refreshing run off sample. Simply tee the red tds probe into the misting line (fitting is provided) and use a grommit or similar to fit the blue probe in the trap or u-bend. This simple arrangement makes it very easy to check and record the in/out ppm at any time. You can gain priceless insights by monitoring the in/out ppm (and ph). Aeroponics is like the ultimate cryptic crossword, you need to find the clues before you can find the answers :wink:


#9

Hey, Atom, happy to hear from you :slight_smile:
That cloner sounds sweet, and good call on the pressure switch, that’s something I will look into.

Learning about what goes on in Aeroponics really does feel cryptic, so I’m glad you are so willing to share your insights with us. That meter looks really useful, so I will have to buy one.

I saw you recommend Hypro AFD series anti drip nozzles in a previous thread, so I’m doing my best to find a way to order those into Canada. Do you still stand by that recommendation, or would you suggest something different for my setup? I know that person was trying to do without an accumulator so I’m not sure.


#10

I wouldnt use hypros in a chamber less than 12" deep, ideally 15"-16" if bottom mounted. If you cant find hypros in canada you can have some shipped over but the postage will cost more than the nozzles :wink: As a guide, 10 hypros CAN$ 31.35 , postage CAN$ 33.95. They would have 1/8 bsp (28tpi) threads which may or may not be an issue. I know npt is standard in the states but im not sure about Canada. In any case, you know there is an option if push comes to shove :wink:


#11

Alright, I ordered them. So you’re saying I should build a bigger chamber right? :wink: Thread size should be correct.

I was going though your post histrory and saw a picture of a system you had built for hpa potatoes last year, did you ever get that to work? I’m interested to know if aeroponic conditions really are superior for all roots.

edit: My order was canceled, A minimum order value of $150 is required for exports to Canada from kscdirect.com. Not really sure what to do now, was there a different website you were looking at? Any other nozzles you would recommend?


#12

It was too late in the season to run potatoes but i did manage to test them out with some surplus toms. They did ok considering they werent buried. With a bit of luck i`ll have them all dug in and ready to go for the upcoming season…assuming we get one ;).


#13

Ah I see, good luck with the season, looking forward to seeing the results!


#14

i know nothing about this, so this may just seem like a random comment. But could your brass clogging be caused by being corroded by the nutrient solution? Perhaps brass is not the best metal to use for this? Aluminum or Stainless Steel a better choice? (maybe even switch to plastic if such exists?) Just a thought. I could be completely wrong.


#15

Hi BioLumo
The brass patio misters are very prone to partial clogging, most have a central stainless steel insert so only the body is brass. They seem to be the most common nozzle that everyone buys…once :wink:
Tip: Dont bin the clogged nozzles, they come in very handy for projects that need a grub screw. Just tap a 10-24 thread and screw them in by hand,


#16

Hi Tino,

Great pix - thanks for sharing.

I have used those small misters shown in the picture and they DO clog regularly in my direct pump fed system (using Aquatec 8855). When I switched to the longer two piece cleanable anti-drip kind that have a spring I found that they clog way less often. Currently, I am using 0.20mm/0.006" (200 microns) with about 120-140 psi. AZ Cool Mist sells them with high-pressure springs so you have to specify/ask them for the low-pressure springs which kick open at about 80 PSI. The supposedly create an average droplet size of 1.4 to 37.9 micron and on average 12.7 microns.

With all that said, I have to add that I am using a 80 micron strainer (100 mesh from VacMotion) on the intake line for the misting rig. This works well and means that I can go weeks without clogs. In order for that strainer to not get overwhelmed I circulate the nute mix through another 80 micron strainer which all in all seems to work. I have tried using finer strainers but stronger pumps break the mesh; or the main misting pump can’t create enough of a vaccuum. Coarser strainers lead to frequent clogs.

Hope that helps.

BTW, where did you get the 2-gallon accumulator tank?

Domenico

PS: Also using Arduino.


#17

Hey Demenico,

Hearing about more working setups helps, I will look into the strainers. Thank you.

I purchased my accumulator from a listing on ebay, it’s this one.