How to build a 750 GPH AIr LIft?

piercho

piercho

New member
I'd like to see if it's feasable to build an air lift that will move about 750 GPH using PVC pipe and off-the-shelf diffusors. These are my parameters:
Max lift column height: 4'5"
Max lift column diameter: 6", 4" preferred.
Inlet/Outlet piping: 1"
Water height differential: minimal. Dumps to a second tank plumbed common to the main.

Please suggest a pump and diffusor set-up. I'd need to get additional air volume from the same pump for a 5'X4" CC skimmer.

Any insight on where to buy piston air pumps (I assume I'll need a piston pump for this) would be welcome.
 
Last edited:
piercho,

Can you give a little more background as to what you are trying to achieve?

It sounds like you want to move water from your sump (under the tank) to the main display tank. I also assume that you want to use air to move the water instead of a water pump in order to protect plankton and other small critters swimming in the water column.

If the above are true, you may want to consider relocating your sump to be level with your display tank. Using air bubbles to raise water gets more and more expensive as the height that the water must be raised increases.
 
There is a tank in a closet through a wall behind the main tank. The water level in this tank is the same as the main tank, and it is direcly connected to the main tank by 1.5" pipe. The equipment normally in or connected to a sump is at this tank in the closet.

Water will flow out of the main tank via a 1" siphon. This is plumbed through the wall into the closet to the bottom of a lift tube. The distance from the floor to the water level of the tank in the closet is 4'5". So the lift tube can have up to 4'5" of lift heigth with 0' head.

The lift tube dumps into the closet tank. The closet tank flows into the main tank.

I guess the best way to picture this is if your sump was beside your tank, and the water level of the sump was equal to the tank, so the recirculation pump has 0' of head. Only in this case the recirculation pump will be a lift tube powered by a very high displacement, high volume air pump.

What I really need to know is what air volume through a diffusor will produce 750GPH of flow with 0' head in a 4'5" X 4" pipe with 1" inlet and outlet pipe. A few hobbyist out there have used these piston pumps and I'm looking for an educated guess on what brand/capacity pump to use with what type diffusor.
 
If I correctly understand what you are trying to do, then by my calculations you will need a butt-load ($$$) of air! :D

Hagen Air Pump

Use a much smaller diameter lift tube than 4". I would not go any larger than 1 to 1.5". As far as diffusors go you may need to leave the diffusors off. Of course this adds the problem of noise and lots of bubbles and splashing. :( but it will move the water.

On the other hand, you may just end up creating the worlds largest protien skimmer!

You may want to search for "screw pumps" on the 'net or see if you can find one on Ebay.
 
I could see the purpose of a smaller diameter lift tube to create head, but in this case I have no head, so I'm rationalizing that a finer dispersion of air in a larger tube will cause higher water flow.

Here is a "for instance" of what type of info I need. From Kevin Carpenter's web page:
"It is powered by a 1/2 HP Sweetwater regenerative blower originally running two banks of (8) 3" diameter by 4 foot tall air-lift tubes. When initially using banks of (12) tubes, over 600 gpm of water flow was measured. "
Since this guy is getting 48 times the volume I need with (12) 4' X 3" tubes, I think I can easily get 750GPH with one single 4' X 4" lift tube.

Help, anyone?
 
First I don't think you want to use an air stone becasue most air lifts I have seen use large air bubbles. www.aquaculture-supply.com sells air lifts and has this table in their catalog. Their air lifts are a piece of PVC pipe with an air collar in it.

1" pipe
Depth 1.0CFM 1.5CFM 2.0CFM
24" 8GPM 10GPM 13GPM
48" 21GPM 24GPM 28GPM

1.5" pipe
24" 16GPM 17GPM 18GPM
48" 36GPM 36GPM 42GPM

2" Pipe
24" 20GPM 24GPM 30GPM
48" 42GPM 48GPM 61GPM


The table has a lot more depths and diameters in it but you get the idea. You can move a load of water with a small pipe and decent amount of air. At 48" lift and a 1" pipe and 1CFM of air you could move 1260GPH. I have a Medo linear piston air pump and I love it.
 
Slightly related to the subject, has there been any usage of the Hydroram device outlined in P.R. Escobal's "Aquatic Systems Engineering: Devices and how the Function" It seems ideal from a feasibility standpoint, but since it's not pervasive in the market, there might be some snags? For those who haven't read the book, the diagram is of a cylinder much like a nielsen reactor with a sealed cylinder 3/4 full of water and a water pump which takes this water from the base and circulates it through the top. Within this circulation circuit is a venturi which introduces air to the cylinder. This air is of course bubbled out of the water displacing the already present air out to whatever purpose you need it for. From a numbers stand point, with a pump that flows 500 gal/hr and specific venturi diameters, this device could drive about 6.22 psi and 600 cubic inches/min. OF course this is all on paper....
 
Snailman: Perfect! I'm downloading their catalog as I write this. Any idea what volume that medo puts out at 4'?

Everybody else: thanks for the input, it all helps.
 
Stephen Spotte in Seawater Aquariums, the Captive Environment, 1979, has a great treatment of airlifts. Here's where having a library of pre-reef aquaium books can be useful. :) His tables yield answers much more conservative than those posted by Snailman.

Spotte goes all metric and my conversions are approximate, but to get 750 g/h with a 4' lift you want about a 1.25" diameter tube and you need to feed it ~2 CFM of air.

The water/air ratio is related to the length/diameter ratio. A longer, narrower pipe is more air efficient. Ideally you want at least a ratio of 40 for length/diameter-- more if you're less than 90% submerged, less if you're 100% submerged. In this example you can get by with a bit less air if you use a pair of 1" tubes instead of the 1.25".

The important thing about bubbles is to try and get uniform size. A small bubble isn't necessarily better. Besides, you probably don't want it behaving like a skimmer.

Here's another web site selling airlifts and high capacity pumps: Aquatic Eco-Systems.
 
If you havn't done so already, you should run a calculation on the head loss on (a) the 1" feed into the airlift and (b) the 1.5" return pipe. Depending on your plumbing, the loss in the 1" pipe could reduce your water flow significantly (1" of head loss is equivalent to reducing your submergence by 1").

If you're relying on gravity to keep your water levels the same in both vessels, you may find that a 1.5" return isn't enough, particularly if you have lots of bends. In this case a 1" head loss would yield a 1" water level difference.
 
Still more useful info. The smaller lift tube diameter makes this easier. Thanks.

It seems like the smallest piston pumps put out ~1.8 CFM at 4', so I'm not that worried about being undervolumed, air-wise. Cost is $150 at pet warehouse for such a pump but I hope to find a better price if I do this.

I was going to size the plumbing the same as I would for a closed loop water pump plumbed for low head/high volume at 750 GPH. I'd like to use bigger pipe for plumbing but then the plumbing becomes cumbersome and obtrusive in the tank.

Watt-wise, I don't think I'll do any better than a water pump in this configuration. Efficiency would be much better if the lift was in the tank (no plumbing loss) but I need to be able to elliminate bubbles.

My objective was/is to boost gas exchange in a low-flow (lagoonal) tank without using a venturi skimmer. Everyone's help is much appreciated, especially the examples and references. It looks like this is feasable if I get the motivation to see it through.

Thanks, Howard.
 
I got "Seawater Aquariums" 1979, Spotte. For a 4', 100% submerged lift, 1.5" PVC is optimal. This lift will generate a maximum flow of 19.4 GPM with a 2.16 CFM air flow. Spotte recommends I derate 25%, or 14.6 GPM = 874 GPH. This allows me no more than 17% loss in my collection tank and plumbing if I am to achieve 750GPM net flow.

Spotte says that uniform bubble size promotes lift effeciency. Smaller bubbles promote gas exchange, a primary goal here. He has lots and lots of references to imperical studies to back up his data.

AquaCulture.com rates its 4' X 1.5" lift at 42 GPM for 2 CFM air injection. I'm not disputing their claim at all, but will note it's double the flow from Spotte's calculation. The lift isn't pictured in the catalog I downloaded. The lift does appear in the most recent price list.

Just for completeness.:)
 
One last question, and I believe that SAT has already answered it, but being a little anal I like to double-check:

If I have a total of 0.4' plumbing head at the desired flow, and am using a 4' lift, then my effective submergence is 90%, yes?

Gotta run and see the little wife play at the Christmas service... and MERRY CHRISTMAS to those of ya'll that celebrate. Thanks for your help,
Howard.
 
I would stick to Spotte's numbers because he is not selling anything but the book. :) If you build this please take pictures and measurments and let us know. I have been interested in air lifts for a long time. I have a good library with some older books but I do not have that one. :( Does he talk about design of the lift like how many and what size holes to put in the air collar?
 
Snailman: I got the book through the WA state inter-library exchange. I can assist if you'd like the information from the air-lift section.

He shows a cut-away view of a manufactured air lift. Basically uniform-sized holes drilled through pipe with the holes distributed in a array. A collar fits over the array and the air hose nipple penetrates the collar. He does not discuss the best hole size for pipe diameter, unfortunately. He stressed that the bubble size be uniform to reduce turbulence in the lift column.

Most of the data available for Spotte to derive his formula from was from industrial-sized lifts. Perhaps someone has engineered more effective small-scale lifts in the 23 years since this book was published. Perhaps they are just blowing smoke.:)
 
Thanks for the offer. If you have a scanner and could scan the necessary pages in a standard format and email them to me I would appreciate it. I have several of his books so I will keep my eye out for this one too. :) The airlift you describe sounds like the ones Aquculture-Supply sells. The ones that Aquatic-Eco Systemes sells just have two holes in a pipe with a hose barb in each one. My only experiance was with six airlifts I made for a brine shrimp grow out tank for circulation. There is a picture of one of these on my web site in the DIY section. The system was setup per the Plankton Culture Manual. I could not keep the water clean so it did not work out to well. :(
 
As a note, I got a chance to tour the University of Texas (Grrr... I'm an Aggie at heart ;)) Cephalapod Culture Station... Or something like that. They had thousands and thousands of cephalapod culture system... Squid and cuttlefish mostly; they didn't do octos anymore. They had some chambered nautili, too.

They used some big protein skimmers, beds of crushed oyster shell, activated carbon, and these big methane powered denitrification towers for purification.

And everything was run by airlift! I'm not sure exactly how they did it, but I know it involved huge central airlift towers and big pumps. :D

-Jon
 
piercho,

Any way you could forward me the information you sent earlier to Snailman on airlifts? My e-mail is in my profile. Thanks! :)

About a year or so ago I was using them on a "ghetto prop" tank for some of my spare corals and I've thought about setting it up again sometime now that I have a Medo pump to run it properly. :) I've been working on and off with them and I'd love to read up on them further so that I actually design it appropriately. FWIW, if you'd like to see my ghetto prop tank, it's on my website: http://www.liquidreef.com/ under the Prop Tub link.

Shane
liquid on #reefs, #reefcentral
 
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