A few pics and data from my HPA system

ethnobotanyFebruary 21, 2013

HPA = High Pressure Aeroponics

I have another thread here that lists all of my parts used for those interested. See a link to that page at the bottom of this post.

In the picture above, the numbers correspond to the following:
1. 2 Gallon Well-x-trol accumulator
2. 125 psi pressure relief valve
3. 12 V Solenoid
4. Pressure Gauge
5. Pressure Switch set to turn the pump off at 80 psi
6. Aquatec 8800 RO Boost Pump
7. 200 Mesh Inline Filter

Results put simply:

1.) 9 plants (6 peppers, 3 tomatoes) consume 20 gallons of water every 10 days during flowering

2.) 0.7 EC has been necessary for the plants to thrive

3.) The 9 plants consume about ~0.2 EC every 3 days during flowering and fruiting

So far this system has been effective and pretty much hassle free. Most people say the main problem with these systems is that the sprayheads get clogged quickly by salt buildup, but I have not found that to be the case. After ~60 days, I have not had any clogged sprayheads from salt buildup. However, I did run into an algae bloom that ended up accumulating at the sprayheads which required me to clean the tubes (took a good hour).

Please, comments or questions?

How does the consumption of water compare to your NFT or DWC systems? Studies have shown that HPA can use 98% less water than other means so I am interested to see the difference, if any at all : )

Here is a link that might be useful: HPA system parts

This post was edited by ethnobotany on Sun, Mar 24, 13 at 19:32

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Looks nice. how much did you end up spending on it? do you have sprayer heads between every plant site?
Normally when you EC diminishes it means you nutrient solution is not strong enough. What causes you to only be able to run the system with an EC of 0.7?
Was it easier or harder to get running than you expected?
I can't speak to during flowering, but I believe while bearing full fruit, my tomatoes consumed 1/2 gallon every 3 days per plant.
Ps: you should put a link to the original thread where your layed out all your parts.

    Bookmark   February 21, 2013 at 4:18PM
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Thanks for your interest Grizz!

Yes, both sides of every plant site has a spray head.

It ended up costing an unknown amount haha. It was kindof spend money here, there, this week, next week, get gifts, etc. In total I would say maybe $300-400.

What causes you to only be able to run the system with an EC of 0.7?

I have been using lower EC levels because research also shows that HPA use up to 75% less nutrients. I can actually increase it with no problem, in fact at one point I did have it over 1.2 EC but I wanted to see how the plants did with less (to save money, and also to try and see if the stuff I read is true).

The system was pretty simple once I understood all the parts, but it took a few weeks of reading to gather enough good information to build the system. I feel if someone was given a parts list and a run-down anyone could build this and maintain it. Taking apart the pieces to clean algae can require patience but it isn't difficult.

Thanks for all the tips, I actually didn't know that plants should maintain the same EC in solution under ideal conditions.

I will add that link now to the original post.

So it seems as though your plants have actually been using less water than my HPA system. Confusing, but difference in the time of the life cycle may account for that. I could have sworn my toms would go through a full 5 gallon bucket every few days when full grown but then again, I never logged that information as I should have. I really need to run an experiment under the controlled conditions for DWC vs HPA and see the difference. That may be my goal for this spring/summer actually.

This post was edited by ethnobotany on Thu, Feb 21, 13 at 16:46

    Bookmark   February 21, 2013 at 4:41PM
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I think it is really a great idea. It seemed a bit overwhelming to configure or I may have shown some interest earlier.
So now that it is up and running;
what is your mist cycle?
Did you just buy a simple cycle timer and modify it to run a solenoid?
How often does the pump run?
What size was the accumulator?
Are you recirculating or run to waste?
Sorry for so many questions. I haven't had a chance to go back and re-read your original post about building it. Plus I know how sometimes what you end up with is a bit different from what you originally planned.

ETA: HERE is a link to your original HPA planning thread.

This post was edited by grizzman on Fri, Feb 22, 13 at 7:34

    Bookmark   February 22, 2013 at 7:26AM
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What psi are you running at?

Salt won't clog the misters, but algae will, like you said. Usually it is non-plant material like bits of silicon sealant or styrofoam. The wire inside of a twist-tie is a handy thing to use to poke out clogs.

    Bookmark   February 22, 2013 at 12:27PM
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what is your mist cycle?

Right now my misting cycle is 1 second on, 3 minutes off. I chose this cycling because I read 1 second on times is most efficient, and 3-5 minutes off is ideal. I may mess around with this timing later, now that I know that the rest of the system works properly.

Did you just buy a simple cycle timer and modify it to run a solenoid?

I'm using the ART DNe recycle timer that has down to 1 second on setting. If you were able to build a timer that can get close to 1 second intervals without buying this timer, you would save at least $50 which would help in keeping costs lower. This is hooked to a solenoid and operates fine. Since there is a few feet between the solenoid and misters, the on time is a little more than 1 second but its nothing I am worried about.

What size was the accumulator?

I am using a Well-x-Trol 2 Gallon size accumulator. It was easy to get to the right psi setting, just requires a bicycle air pump with an air pressure gauge. With this size the pump runs every 1.5 hours (havn't actually timed it, this is an estimate) or so and only runs continuously under 5 minutes to fill the accumulator. I decided on this size for the fairly cheap price (I think it was about $50, maybe a bit more) compared to larger sizes, and I also know that if you have too much solution in there under pressure, and it sits for awhile, it can become stagnant and make cleaning the system take far more time since I would have to wait for the entire accumulator to drain to rune water/bleach through it.

Are you recirculating or run to waste?

I did try this. The system would remove about 5 gallons of water per day under drain to waste conditions. This for me was way too costly for nutrients, even at 0.7 EC. Given a 20 gallon tank I used closer to 75 mL of each individual g/b/m total every nutrient change.

I actually have the system rigged so all I need to do is rotate a few t's and I have a drain to waste system, which is going to be nice for cleaning the system out with bleach and running Flora Kleen the week before harvesting fruit.

No problem with the questions, I am more than happy to share knowledge about my system and actually enjoy it.

@ CR

What psi are you running at?

Im running an average of 70 psi in this system (the pressure switch stops the pump at 80 psi, and the pump kicks on at 60 psi)

Also, to combat the issue of small particles clogging the misters I am using the 200 mesh inline filters as suggested. Algae is really the only thing able to bypass and clog, except for tiny particles from cutting the RO tubing when I made the system.

Also, good idea about the twist tie! I will have to see if it is small enough, so far I've barely been able to clean the misters with the very fine tip of needles :-S

    Bookmark   February 22, 2013 at 2:30PM
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I was thinking with the drain to waste idea, you could run it drain to "waste" but actually catch the waste. Then each day switch out the reservoir.
With the waste from the 1st day, readjust the pH and EC and put it back into the rotation at the end of the second day while you're readjusting the second reservoir.
That way you're not really losing any nutrient and at the same time not trying to adjust it in the system.
That's a cool system. I may have to look into investing in one.

    Bookmark   February 22, 2013 at 3:52PM
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Good ideas and thanks, Grizz

    Bookmark   February 23, 2013 at 10:55PM
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Hi Ethno
Drain to waste is a very viable option for hpa. The fence posts arent the best choice for hpa. A large chamber will use fewer nozzles as there`s more space for the mist plume to develop.

The other thing i noticed from the thread is your nutrient usage is much higher than expected, Your accumulator is running for 1.5 hours when it should be doing around 6.
To see what i mean here`s some calculations based on the numbers in the thread
A 1 second / 3 minute cycle timing is equal to 485 * 1 second mistings per day or a single misting of 0.1437 hours.
Sixteen 0.8gph nozzles have a combined flowrate of 12.8gph.

Total amount of nutes per day = 12.8gph * 0.1437 hours = 1.839 gal.

Possible causes are timer inaccuracies, mist overrun (nozzles continue to spray after solenoid closes) and inaccurate nozzle gph from the manufacturer.

Just for the sake of being thorough, here`s the numbers for your accumulator,
Refilling the 2gal accumulator from 60 - 80psi should take around 4 minutes and 12 seconds if the pump averages 0.38L per minute. If your air precharge is 58psi, you`ll have around 0.15L left in the accumulator when the pump starts (60psi) and around 1.75L when its up to 80psi.

This post was edited by hex2006 on Sun, Mar 24, 13 at 3:23

    Bookmark   March 24, 2013 at 3:20AM
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In one of you picutres you show you parts with numbers beside them. could you tell us what the various parts are according to the numbers?

    Bookmark   March 24, 2013 at 4:57PM
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Grizz, I updated the picture to include a parts list below.


Thanks again for the input. I am avoiding dtw because my system is indoors and I don't currently have much space to put a third container anywhere for the waste solution. But, if I ever run into a larger area I would prefer dtw for the fact that clean solution is only what the plants get, no re-used stuff.

As for the calculations, I completely agree, something is not quite right. Its one of those things where I spent a good amount of effort and money to putting this system together, and just the mere fact that it works and grows plants has been amazing to me.

But you're right, the accumulator fills way too often. I think the issue may be multiple things. One thing I know attributes to greater flow than 0.8 gph, is that the sprayers I use shoot out streams of water once the solenoid shuts and pressure goes down. This, obviously, increases the amount of flow. Maybe up to another whole second of on time equivalent flow (0.8gph). Moreover, the timer is accurate down to 1 second, however, the solenoid is situated a couple feet worth of hosing before the sprayers, so there is a definite lag time before the sprays shut-off, making the actual on time at least double 1 second.

This means, for calculation purposes, 3 seconds on time.1 additional second for the "lag time" between solenoid and sprayers, and another 1 second due to low pressure water streaming out of the sprayheads.

Total amount of nutes per day = 12.8gph * 0.1437 hours = 1.839 gal.

1.839 * 3 = 5.517 gallons per day, which is actually fairly accurate as that's how much I gathered the couple days I tried out dtw to test the flow of water through the system.

Continuing, the pump should run 6 / 3 = every 2 hours under these new conditions. It actually runs more often(1.5 hours), why?, not sure, but there's maybe less water than expected in the accumulator after filling to 80 psi?

How to fix these problems... maybe getting new sprayheads is something I need to consider. What kind do you use? "No drip" nozzles?

    Bookmark   March 24, 2013 at 8:08PM
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Hi Ethno
I use coolnet pro nozzles with anti drain valves. I would say your nozzles have more flow (and run on) when the accumulator is up at 80psi versus 60psi so the tank is emptying faster than you expect. Fitting an adjustable pressure regulator / pressure reducer will keep the output pressure constant.

No drip nozzles will help with the run on issues. You`ll probably need the same number for coverage in the fence posts so the cost vs benefit may be limited. Large open chambers need fewer nozzles because the individual mist patterns spread out and overlap to cover more space.

    Bookmark   March 25, 2013 at 3:36AM
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Right on hex thanks for the info on your sprayheads. Those are 5.5 lph it appears. Did you purchase the soft tubing and stabilizer with them?

    Bookmark   March 25, 2013 at 8:58PM
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I use rigid pex tubing as my system runs at a constant 90psi, (100L accumulator 150psi-90psi, pressure reducer set at 90psi), i dont use the stabilizers which are just weights that stop the assembly oscillating when they turn on. They`re useful for nozzles that hang 12"-24" below the supply tube.
I dont know how well the nozzles would do in a restricted space as they have a long throw full cone pattern. At 3ft from the nozzle, the cone is around 18"-20" diameter, at 4" it would probably only be a few inches. The overall length of the nozzle assembly is perhaps 3", so you may need to get creative with the plumbing.

    Bookmark   March 25, 2013 at 10:57PM
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OK still interesting. If I phase out my gullies and implement larger containers then I might have a go at those nozzles.

Where did you buy them? How expensive were they?

Thanks again.

    Bookmark   March 26, 2013 at 2:18PM
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I got them from a commercial irrigation supply place. They are made in the states so you shouldnt have any trouble finding them.. I dont remember how much but not that expensive considering each assembly consists of seperate parts. a mount, anti drain valve, connector and the nozzle(s).

    Bookmark   March 26, 2013 at 3:35PM
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