Please explain Aero/Hydro pumps and pressure

I understand how hydroponic and aeroponic systems work, and I have a general idea of the parts I need, but I've never seen anyone actually go into detail about the power of a pump (GPH)

and how it correlates to the length of pipes it can go through,

diameter of pipes,

what types of misters to use (some require A LOT of pressure),

etc.

If I have a 20 gallon tote, does that mean I'm aiming at at least a 20 GPH pump? 40? 100?

And if I have a 200 GPH pump, what diameter should the tubes be?

I know next to nothing about water pumps but wouldn't having narrow tubes create back pressure wearing down the pump?

and having too wide would lower pressure coming out of the misters

help ..!

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more info would be needed to answer questions.

such as what kind of system are you speaking of reservoir size doesn't mean anything, however 20gals is a very small reservoir some aeroponics use small reservoirs and just spray the roots overhead. I believe these are generally low pressure aeroponics.

in true aeroponics people use high pressure pumps because the misters bottleneck the flow and 50-100psi pumps allow them to make a mist properly with a small particle size. the idea being your root zones will absorb particles that are 50micrometers in size or less or whatever the case may be.

gph is just that, how many gals per hour of water your pump will move.

I guess you can think of psi as torque in a car. I don't really know much about aeroponics, I'm an ebb&flow guy but I did what I could to help

Ok i ran into this same question a while back and wasn't able to find much info on it till I dove into some technical stuff... To overly simplify the matter; pumps have 2 specs that you care about. GPH and more importantly Head.

GPH is the volume of liquid moved during a given amount of time, and Head is, basically, the max amount of pressure the pump can handle while still being able to move SOME volume. One important thing to remember here is that these two specs are inversely dependent, hence, the volume of output that a pump can produce (GPH) decreases as the Head (pressure) increases. So in terms of Aeroponics, the GPH rating is somewhat useless. Think the paddle wheel on a paddle boat; it can move a shit ton of liquid, but doesn't generate a whole lot of pressure.

Most (i think) pumps are typically rated at 1 ft. of head. So when you roll into the store and spot a pump that is rated for, say, 1000 GPH; (usually) that is saying that the pump can move 1000 Gallons in an hour when the pump output is 1 ft. above the intake. Now naturally, the larger the separation in distance between the pump intake and output, the less GPH the pump can move. Quality pumps will have not only the GPH for a given amount of head (typically 1 ft.) but they will include a graph showing you the GPH at 0 head, all the way up to the GPH at the max head (0 GPH).

This can be demonstrated via the following... grab a pump u have lying around... hook a tube up to it... and turn the pump on. You will notice that the maxiumum amount of flow is achieved when you hold the output tube at the same level (actually below) the intake of the pump. Conversely, as you raise the output tube (in relation to the intake) the flow decreases. If you hold the tube up high enough you will notice that the pump can only push the liquid up so high, and at a certain point it will cease to move any higher, but maintain its height. This maximum height, where the flow is effectively 0 GPH is the Max. Head rating of the pump.

So what does the Head rating of a pump have to do with Aeroponics? Here is the trick... multiply the head spec(in feet) by .45 and the result is ROUGHLY the amount of pressure in PSI that the pump will output.

So in TRUE Aeroponics the goal is to atomize the nutrient solution in a manner that achieves droplet sizes of < 50 microns. To drive any kind of nozzle that can achieve this, you are going to need ATLEAST about 50 psi pressure. If you look at the specs of a nozzle that can achieve this kind of atomization, they are typically rated for very low GPH and high PSI. In Aero you can sustain large amounts of growth with much less nutrient solution because the plants are using it much more efficiently.

Now there are different ways to achieve this pressure needed to get <50 micron atomization. The cheap way to do it is to use a pump with less PSI (still above 50 PSI) and utilize a collector tank to build up the pressure needed. However, this complicates the situation; now you have to deal with a whole bunch of other stuff like regulating tank pressure, sealing a bunch of extra connections, etc, etc. So I would recommend shelling out a few more $ and getting a pump that is capable of producing the pressure you need straight off the pump w/ no collector tank.

Now what kind of pump is that? Well, there are many different kinds of pumps. Most of the fountain type pumps are impeller driven. While these pumps might suffice for fountains they typically cannot produce the pressure needed to run a TRUE Aero setup. If true aero is your goal then you need to look at diaphram pumps. They produce much higher PSI/lower GPH than impeller driven pumps and and are much more suited for aeroponics.

Of course... if you are a cheap bastard like myself... or TRUE Aeroponics sounds like too much of a PITA... you can get a pump like this, http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94648 and get some crappy homedepot/lowes drip irrigation misters like this, http://www.misterlandscaper.com/misters.html and have yourself an ALMOST... TRUE Aeroponics system.

BTW... you can drive those mister's with a much smaller pump like the 500 GPH pond pumps that HomeDepot/Lowe's carries, but the results are somewhat inferior, i.e. you get big fat droplets and NO true "mist".

[edit] also take a look at ultrasonic transducers. They produce a very fine mist (< 50 microns) via high frequency vibrations, and they are a much cheaper way of achieving <50 micron droplet size... BUT I'm not sure how these stack up to true Aero because theres more to it; the most ideal mist is roughly 50 microns ONLY w/ no larger/smaller droplets (i think) & and they also have a static charge which causes them to be attracted to the roots and get pulled right into the "pores" on the root hairs. Actually......... disregard everything I just said n go search "true aeroponics" or "TAG" and you'll find much more usefull info.


....oh yea.... or just click the "DIY Link 'ORama" link above

Great post NS775, very good info concerning pumps.

The only thing I find fault with is droplet size. It has been shown that sub 5 micron size droplets can be taken in by the "air" roots directly, while aprox 50 micron sized droplets can only be utilized by the "tap" roots. At sub 50 you are really looking at fog.

I'm just in the process of setting up a aero/fog grow tray that uses both misting nozzles to produce a wet fog (aero) and a ultrasonic fogger (NOT a pond fogger) to produce dry fog.

I have an album of pics of it, if anyone is interested.

Oldmac: I was going for a similar setup (ultramist + misters) but my ultramist fogger died on me last week. I'll keep up with your progress though!

FreezerBoy: Thanks, but I went through most of the DIY for aero and while they're informative, they don't delve into the technical details. My concern is having a problem like this, quoted from an aero post by Pirate:

Quote:
i have tried those little green sprayers (similar to your yellow ones) before and have not gotten them to do anything, even with a 500 gph pump. I'm thinking i just need higher pressures. But this tutorial really make me wanna break all of that stuff out right now!

reply: I have the green ones.........They are the same as the yellow just by a different company.........They do suck. For LP Aeroponics I have found the Micro Sprinklers to be the best by far. Better spread are and can handle pretty high pressure. If you had 25 PSIs you could get a 25 foot spray circle. Try that with Gro-Clone sprayer.

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Thanks Captain/NS775. VERY informative post, just what I was looking for! Bookmarked.

I was looking into ultrasonic transducers but wondered whether the mist would be able to penetrate the root mass. I mean would just having a bucket with a few ultrasonic transducers grow a monster plant?

NS775 is correct

NS775 is correct

Not that he needs me to say so.

But to simplify matters for you, just remember that for every 2 feet of "Head", you will get @ 1 psi. So, if you want to use misters that are optimally run at 50psi, you need a pump that will pump about 100 foot head pressure.

Start here. Design your aeroponic system and decide on the type of mister (choose misters for the gpm and droplet size) you will use AND the number of misters. Let's say. for example, you found misters that flow at 1 gallons/minute and your design calls for 20 misters. So now you know you need a pump that can pump a minimum of 20 gallons/minute. Now let's say your misters need to run at 50psi (all misters will have the tech spec chart, just look for it) to produce the most efficient size water droplet you and your plants want. (Impeller pumps are designed to move volumes of water at low pressures like in a irrigation ditch to a row of corn... or in a fountain, lifting water only 4 feet high or so which would be about 2 psi. You need a pump designed for pressure and those cannot be bought at Home Depot.)

So, given this example, you need a pump that can pump at least 20 gal/min at 50psi. Always look for a pump that can handle about 20% more then your minimum requirements. It's easier to get a bigger pump and then buy a pressure regulator and install downstream of the pump so the pressure is constant. Just do the math.

It's that simple.

do you guys know where are they selling these 50 micron size misters? bc i can't find them anywhere

Oldmac said:

Great post NS775, very good info concerning pumps.

The only thing I find fault with is droplet size. It has been shown that sub 5 micron size droplets can be taken in by the "air" roots directly, while aprox 50 micron sized droplets can only be utilized by the "tap" roots. At sub 50 you are really looking at fog.

I'm just in the process of setting up a aero/fog grow tray that uses both misting nozzles to produce a wet fog (aero) and a ultrasonic fogger (NOT a pond fogger) to produce dry fog.

I have an album of pics of it, if anyone is interested.

Click to expand...

Will you be using one of those submersible ultrasonic foggers with the replacement disks? If so pre-plan on dealing with the extra heat they will generate in your reservoir. I have one in mine and I had to disconnect it to keep my temps in check.

A mister produces a wide range of droplet sizes which may include 50 microns

howdy!

i worked in the live marine specimen industry for 20 yrs and the "pumps" used in the fish and now hydro industries are usually not really "pumps" at all. centrifugal gear pumps and piston pumps are true pumps with positive displacement. some are capable of developing tremendous line pressure. magnetically driven powerheads are really blowers and, as such, while some can throw huge amounts of water, suffer from every little increase in resistance and back pressure. this can greatly reduce their "gph". head radically decreases volume with each additional increase in height.

plumbing engineers use formulas to calculate pipe resistance to pressure, but generally speaking, the longer it is, the larger the diameter, the more you get.

any restrictive devices in line, like hose nozzles and misters, also greatly reduce flow. therefore it is to your advantage to use the largest possible misters.

turns or fittings in the system reduce flow.

it is a prevalent myth that going up in pipe diameter from your pump outlet will move more water. say going from a 3/4 outlet to a 1" or larger pipe. this actually decreases volume. so, plumb your system with the same diameter as the outlet.

i've never done aero but ran bio buckets, rwdc, and some fairly large (10-20,000 gal) holding systems for fish.

i own 2 950 mag-drives now left over from the bio-bucket days and ran them 24-7 for more than a year without failure. they are still being used intermittently for watering my plants. i like them for reliability and the fact that they have threaded inlets and outlets. i recently accidentally left one on for a day plumbed into a hose and a water wand that was in the off position and not allowing any water movement at all. the next day it fired right up.

they can be found at: www.marinedepot.com in all sizes.

i think that if i were running misters with aquarium or pond type pumps i would buy the largest pump i could afford for the application.

Delta9nxs: I just want to point out that there is no such things as a "centrifugal gear pump" but a gear pump and reciprocating pump is a positive displacement and a centrifugal pump is non-positive displacement pump.


!!!: there are some simple formulas to calculate pressure in your system. Pascal's law states Pressure=volume x area. Volume in Gallons , or cubic inches (there is 231 cu.inches in a gal.) So you would take the diameter of pipe and the length of all your piping. To find the area take your Radius (in inches or feet) squared x pi x length= area in either square inches or square feet.

Also take into account, a flooded suction pump arrangement (reservoir higher than pump) would be better than say suction lift pump arrangement (reservoir lower than pump) for the centrifugal pumps ( most efficient for large volume low pressure). You should plumb your pump out of your reservoir to help keep res temps low.


Grapeman: To calculate head pressure multiply .433 psi by the height by the specific gravity of water (which is 1.0). So to have 50 psi you would need 115 feet of head pressure (50psi divided by .433 X 1). But remeber pumps come with a pump specsheet that tell you how much Net Positive Suction Head atmospheric pressure you need in order to obtain the proper output at the pump outlet. You dont neccesarily need 115 feet of head to obtain 50 psi from the pump. The pump spec sheet will tell you.


So when you find out the pump specsheet, you factor that information, along with the volume and area of your whole system, and then you would find the spec of the micro sprayer you want to use. When u have all three of these numbers you have just set yourself up for proper aeroponic application.

manitobagrower, thanks for fixing that. i was in a big hurry this morning and thought that was the name of a type of pump i used 25 yrs ago. i can remember taking them apart all the time to remove trash from the gears. and, thinking long and hard about them, they could not have been positive displacement. they still threw water hard enough to knock you down if you stepped in front of it.

thanks again d9

I bought a great small grower high pressure system from www.reptilebasics.com It is the Advanced Mist System ($199, including a proper timer) with an Aquatec pump. {3/11: Ed: You need a much lower cycling timer ~ < 4 seconds)

Their double and quad heads are easy to mount and provide a very nice fog. Didn't find them until my grow was almost done, but they work great. I am looking forward to starting out with them on my next grow.

FYI I tried ultrasonic foggers- too many hassles- like heat, can't handle > 400 ppm nutes, discs burn out fast.

WarBux said:

Will you be using one of those submersible ultrasonic foggers with the replacement disks? If so pre-plan on dealing with the extra heat they will generate in your reservoir. I have one in mine and I had to disconnect it to keep my temps in check.

Click to expand...

Those are "pond foggers" and no I am using a FrapaPlas fogger.

PetFlora just pointed out a FYI about them. I would add to his list the problem of the fog clinging to the water and only rising a few inches off the water, so some sort of a fan is needed to move the fog around.

Also, people should check out PetFlora's link, the advanced mister pkg is an excellent starting point for a true aero sytem. The Aquatec pump is very similar to the SurFlo 8035 pump I'm using for the areo side of my system. I actually have a Aquatec 6800 pump in my system, but it is used to transfer nutrient solution to the fogger.

ManitobaGrower said:

Delta9nxs:
Grapeman: To calculate head pressure multiply .433 psi by the height by the specific gravity of water (which is 1.0). So to have 50 psi you would need 115 feet of head pressure (50psi divided by .433 X 1). But remeber pumps come with a pump specsheet that tell you how much Net Positive Suction Head atmospheric pressure you need in order to obtain the proper output at the pump outlet. You dont neccesarily need 115 feet of head to obtain 50 psi from the pump. The pump spec sheet will tell you..

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While I appreciate your accuracy, I wasn't asking a question. I've designed and installed hundreds of acres of irrigation lines and equipment, and i suppose I have hired folks like yourself over the years to crunch the numbers for me.

I was using a rule of thumb that 2' of head equaled @ 1 psi. No need to try to point out that I was off by few 100's when I was speaking in generalities, unless you felt the need to do so for yourself.

Fan indeed!

One of the problems with UF is that they lay just above the surface and you need them to circulate. In my first attempt to circulate them, I directed a small fan into the res in order to blow the ultrasonic fogged nutes up. Later, I added the spraybar; when I ran themm both at the same the fog circulated around the entire grow chamber. Check out my Journal for a TAG grow/DIY frame- 2 X 4 x 6+

Not reading other people answers, but Aero requires a lot more pressure to get a fine mist as well as unclog itself....for ebb and flow, or just a table that .......well what I did was drill holes through an ebb and flow table to have plenty of air stones under the roots and not in the rez....then just ran the ebb and flow table 24/7.....so it was like a deep culture but it wasn't that deep...

Go for a better pump and watch out for the aero...those fine mist nozzles create problems and even with a table...well roots clog drains and that is a problem if you cant get into those...without picking up the table cover which means your plants and that sucks.

Sorry grapeman no offense intended, i was only trying to point out a more accurate figure as a tradesperson and personnally i do not like generalities as mathematics is a langauge in its own with very specific figures and the term "rule of thumb" came from england when it was legal to hit your wife with a stick no wider than your thumb. again i apologize.

ManitobaGrower said:

Sorry grapeman no offense intended, i was only trying to point out a more accurate figure as a tradesperson and personnally i do not like generalities as mathematics is a langauge in its own with very specific figures and the term "rule of thumb" came from england when it was legal to hit your wife with a stick no wider than your thumb. again i apologize.

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Hey - my reaction was a bit strong. Sorry also. I'm dealing with your trade at the moment on a 500 acre piece where I have to pump water to a 5 acre cement lined reservoir on the property about 1 mile away and up a 130' hill, then transferring the water to a second cement lined reservoir on a 160 acre property 2/3 of a mile away. The water district delivers water in cubic feet/second while our needs are measured in gph, depending on the various water needs of the different plants/vines/trees in their varying stages of growth projected over the years it will take to develop the farm.

So I do appreciate your detail accuracy on projects like this. For a 20 bucket grow, I use "rule of thumb" and round upwards on the pump so I don't get a headache with the math.