Adventures in Hydro #2 - LP Aero/NFT mash-up - or - switching to HPA?

Same here. How you doing Larry?

Hope the absence is caused by you having loads of fun n stuff :wink:


Same here, was just thinking of him yesterday and how I hadn’t seen him around. Hope all is well brother!


Thanks guys!! I really do appreciate the sentiments - seriously - thanks!!!

Sorry for the long absence. I have been under the weather with various things - the worst of it a series of kidney stones - and generally very busy other wise. The result is I have just been too tired or tooooo stoned to post anything coherent :slight_smile:

Im off to bed now, but I will be back! :slight_smile:


Good to hear from you. Get well soon!

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Glad you’re still around buddy! Hope you start feeling better, I once had a bout of kidney stones that put me in the hospital for a week – horrible little things.

I’ve got incoming clones for the HPA room and I popped 5 beans 2 days ago for the veg tent, so I’m about to get rolling again. Would love to have you along for the ride and insights. :slight_smile:

Take care of yourself and feel better man…


Hi Larry and all contributors to such a great topic!

I read all 700+ posts (it was not so easy :slight_smile:) and would like to thank you all for such a broad experience you described.

I’m trying to master aeroponics growth, but unfortunately my roots still looking more hydroponics, than aeroponics.

Here is brief info about my experiment:

  • plant: basil
  • pressure: 6-8 bar, water accumulator
  • nozzles - orifice 0.3mm, full cone, attached to the relay
  • growing in the hollow tube, one nozzle shoots down from the top of the tube
  • PH - 6, EC - 400 PPM
  • misting cycle 2sec on / 3 min off
  • drain to waste

Plants are looking nice, but there are no aeroponic roots -> no aeroponic growth speed.

Could you please advice what I’m doing wrong?

Many thanks.

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Sorry, I am still running around like crazy with little time for fun stuff. I hope to have some free time by this weekend.

In the mean time, the only thing that jumps out at me is your timing cycle. It sounds to me like you have way too long an ON time followed by too long an OFF time.

I have been running well under 1 second of ON time and never over 2 minutes off time - mostly less.

However, we need more info to help dial this in better. How much volume do your nozzles put out on each ON cycle? Have you been watching the roots to look for signs like large droplets collecting on the roots? Have any close up shots of the root hairs? How big are those tubes - how long and diameter? What is the cone angle on those nozzles?

Sorry, got to run, but I will be back…

Oh - also very important - how many nozzles and where are they placed? Pressures? Any idea on hang time for the mist?

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Good, I’ve missed your detailed posts. You got a new round going yet?

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Hi Larry,

Thank you for your fast reply, and apologizes for delay. It was a very tough month.

So, basically, I have a tube. On top of this tube, there is a nozzle directed downwards. There is only one nozzle per tube. I read your posts about on/off time, but unfortunately I cannot afford such a short period of misting. I have only one nozzle per tube and it takes some time to fill in the whole tube with a mist.

Here is a sketch of an idea. Black is a nozzle.

Info about nozzle:

  • nozzle diameter: 0.3mm
  • full cone, 60 degrees
  • pressure: 8 bar
  • water consumption: 0,034 l/min

Tube info:

  • Height: 2.5m
  • Diameter: 400mm

So, it sounds pretty nice, but there is no well-build lateral system. Moreover, after a month it seems that plants are trying to build their roots as much long, as they can, while canopy stays underdeveloped…

There are a few droplets on the roots, but mainly they are not overwetted.

Here is a video of misting cycle 2 sec / 150 sec, bottom of the tube:

Theoretically, I may start making a short pulse (<1sec on, <1 min off), but there are also periods in the beginning and at the ending of the pulse when the pressure is not 8 bar (maximum), and there are a lot of large droplets during these phases. To minimize these starting/ending phases, I decided to use more long shots. Do you think shorter pulses would be better?

Also, I’m waiting for 0.1 mm nozzles (trying to avoid starting/ending phases)

Thank you in advance

It seems like there are several things here that could be improved, but Im still not clear on the construction of your system, so I have a few questions.

In the picture, that tube looks like its square - or is it round? Im asking because Im trying to calculate the total volume of the chamber. We need that number so we can see if you are putting enough mist into it on each ON cycle. Im assuming it is 2.5m long by 400mm wide by 400 mm wide? That gives me a total volume of .4 cubic meters? Is that correct?

Looking at your video, I see what you mean about the large drops at the beginning and end of each cycle. That is usually because you have the solenoid too far from the mist nozzle. It could also be from tubing that is too flexible, etc. Do you have any pics that show exactly where the solenoids are in the system and all of the parts and how they connect?

Also, are you using a pressure regulator or reducer of any kind to keep the pressure constant at the nozzles?
Do you have an accumulator tank or are you feeding the nozzles directly from a pump? Both of those can make a big difference in the quality of the mist.

If you are going to do drain to waste, then those large droplets are killing you. They are just wasted nutes.

From the video, if that was a 2 second ON cycle, Id guess that the first 1/2 second at least is wasted, plus more on the tail end, so Im guessing you are only getting maybe 1 second or less of good mist out of that 2 seconds of ON time.

The next thing is your off time is way too long. You can see the mist is pretty much all gone well before the next ON cycle starts. The goal here is to try to have the mist stay as uniform and constant as possible in the chamber. You do NOT want the roots to get wet and then dry out. They need to be kept, as much as possible, at a constant level of wetness,

I need to run, but quickly - I think the mist from your .3mm nozzles looks good.

Im afraid the .1mm is going to be too fine a mist and wont help the big drops at all.
other things are causing that.

More after you get me some more details…


Great thread, will definitely be using this for reference if/when I decide to go hydro…

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Basically, it’s a tube. Here is an animation of how it looks like:

Total volume: .8 cubic meters. (sorry, I gave you not correct dimensions)

As for the droplets at the beginning/end of the cycle – I attached the nozzle directly to the relay. So, there is no pipe between them. Unfortunately, I do not have a proper photo at the moment — only this one from the top of the tower. A nozzle straight screwed into the relay.

I also have an accumulator tank, good pressure control (it varies from 7 to 8 Bars) and drain to waste.

So basically everything should work properly, but that large droplets during the pulse (at 2:20 on the video) drive me crazy… I understand that AA nozzles are the best solution (uniform spray), but you got such outstanding results using only pressured nozzles.

Thank you a lot for the comment about timing! I thought that it’s ok when a mist almost gone at the end of the pause. I’ll decrease OFF period (maybe twice) and then will play around ON period.

How about the night shift? According to Atom, we should increase the OFF period almost twice. In this case, mist definitely evaporates at the end of the cycle.


Sorry for the slow reply - Ive been in and out of the ER and dr offices the last several days - more dang (huge) stones!

Ok, I have another questions or two.

If the nozzle is directly connected to the solenoid, then pressure drops in the tubing is not the issue - at least not the way I thought at first.

You have an accumulator tank, and the pressure in the system is 7 to 8 bar, but I need a few more details.

Is that 7 to 8 bar the pressure in the tank itself or the pressure feeding to the solenoid? In other words, is the pressure in the tank the same as the pressure feeding the solenoid? The question Im trying to ask is - are you using a pressure reducer between the tank and the solenoid or is it a straight feed between the tank and solenoid?

What is the volume of the tank, and is it a metal tank or plastic?

Do you have a pressure gauge hooked up between the tank and the solenoid? Preferably close to the solenoid end of things? If not, can you add one?

Next question is about the nozzles - are they anti-drip?

Here is my current thinking on the large drops. It could be two things.

  1. It sounds like your nozzle does NOT have an anti-drip valve built in, or it isnt working. The first sets of nozzles I bought had bad anti-drip valves.

I think one thing that may be happening is the nute water in the down facing nozzle is draining out during the OFF cycle. That will cause a delay in the start of the mist while the nozzle fills up again, and cause the pressure to build up more slowly during the start of the ON cycle. That will cause the large drops at the beginning while the pressure is too low.

  1. The next thing is if you are NOT using a pressure reducer, and/or you have a long tube between the accumulator tank and the solenoid, the pressure in the accumulator tank will drop a lot during the first part of the ON cycle. A long flexible tube between the accumulator and the solenoid just makes it worse.

A pressure reducer will help keep the pressure more uniform - especially if its mounted close to the solenoid. The only way to know for sure is to put a pressure gauge right at the solenoid or as close as you can get. Then you can actually watch the pressure fluxtuate up and down during the ON/OFF cycle.

With no pressure reducer, I was seeing 20-30 PSI of pressure drop during each ON cycle. With the pressure reducer it is down to less than 5 PSI. Also, ANY air in the lines will cause the same problem.

Your chamber volume is huge for a single nozzle to fill. Im also guessing your nozzle is a wide cone shape. Do you know the angle?

If it is a wide angle cone, much of your mist will be hitting the side walls before it ever gets to the bottom of the chamber. A nozzle with a very narrow cone would be better for your situation.

I totally misunderstood the size of your chamber - it is much larger than I thought. Yours is almost 5 times as big as mine is, so you will need 5 times the volume of nutes for each ON cycle.

I was using 4ea 0.5mm nozzles in a chamber 0.17 cubic meters. Im guessing based on the specs for my nozzles, that your 0.3mm nozzles put out about 0.4 GPH. Mine put out 0.9 GPH.

So I have nozzles that have twice the flow rate yours do, plus I have 4ea and you have 1ea. plus your trying to fill a chamber that is almost 5 times as large.

That means you will need somewhere around 40 times as long an ON cycle as I was using. I think I was averaging around 0.7 seconds of ON time, so you may need as much as 28 seconds of ON time to truely “fill” your chamber from top to bottom.

I am on some good drugs at the moment, so no promises, but if I am doing all the math correctly - you may need as much as 28 seconds of ON time. That doesnt seem like its going to work very well for that tall a chamber and a single, wide cone nozzle. The plants at the top will get over watered if you run the nozzle long enough to get good mist at the bottom. Thats also where a narrow cone nozzles would help. Micro sized water droplets dont bounce - they stck to the first thing they touch, so a wide cone will waste a lot of mist on the upper parts of the chamber.

I would suggest you do some tests.

First, measure the actual flow rate using the plastic bag trick I described above.

Next - make any changes based on the questions I asked at the beginning about the anti-drip nozzles and pressure reducer, etc. Also the pressure gauge test.

Then, put a camera and light down in the bottom of the chamber and fire the nozzle. See how long it takes for a good level of mist to show up down there. Id start with that time as an ON time and adjust from there. Keep in mind that when the chamber is full of pots and roots, there will be more blockage slowing the mist.

No matter what you do, you are going to end up with a compromise situation if you only have a single nozzle in that tall a chamber, but you should be able to get it working much better.

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Quick up-date on my growing plans.

Im still on the fence as far as up-grading to an Air Atomized system or staying with the HPA. I need a new pump and some other parts if I stay with HPA. Switching to AA will only cost me an extra $50 or so - BUT - that assumes I can find cheap nozzles that work.

I found some inexpensive air nozzles on Amazon, and ordered one to play with. Total cost was around $25.

A single nozzle will likely be enough for my size chamber, but I wont know till I can do some testing. Im actually hoping the flow rate can be dialed down enough so I can use two - for a better mist spread.

I have two old, very noisy contractor air compressors I can use for testing. If the nozzle works ok, I will probably invest in a quiet air compressor.

Once I get the nozzle and start doing some testing, I will start a new thread for that. This one is just about long enough :slight_smile:

I dont plan to start my next grow for at least another two months, so I have time to play around.


The air nozzle arrived to day, but it doesnt work.

Either they sent me the wrong one, or this one is defective or they have no clue what the word “siphon” means.

When I hook it up to the compressor and a small tank of water, it just blows air out of the liquid intake port. Kind of hard to siphon water when the air pressure is positive instead of negative. Ive emailed the seller and wil have to wait to see what they say.

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Hi @ReikoX, I somehow missed this when you originally posted it. Are you saying that processing UN-decarbed bud will yield that THC-A?

Im assuming you dry it as normal first, then do the regular tincture processing with EverClear?

Im going to have to try that. I just found maybe 50 gms or so of bud I left sitting in an uncovered coffee can on a shelf. Its mostly popcorn buds, but its plenty dry now. Its been sitting on the shelf for around 5 months.

Yes, that’s exactly what I’m talking about. :+1::seedling:

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Pretty nice set up

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