Thread: Airlifts - pumping water around a gravity system using only air

Originally Posted by noo

Hello Nick, thanks for chiming in.
I wanted to copy the 5 or 6 inch external air compression chamber on 110mm uplifts like everyone else but it's not easy to source those parts where I am. See A of my diagram

I am able to step down from 110mm to 90mm fittings easily with an internal air compression chamber but that would create a restriction of the 110mm pipe diameter with a reduced flow. See B of my diagram. What I was trying to determine is how much of a reduced flow.... ? The reduced cost, ease of parts and time saving may be worthwhile as I could add another airlift to make up the difference.

However, I have settled on option C of my diagram using a 110mm TEE and putting the air diffuser below and out of the water path. So I can keep the 110mm pipe diameter and reduce costs and not have to import bits from across the world.


Attachment 43729

Hi

I was able to build an air chamber fairly easily...

I used 2 x flexible clay to plastic rubber boots from Toolstation: https://www.toolstation.com/fl...ble...-to-pvc/p54240

And for the main wall of the air chamber I used a 125mm pressure pipe straight socket from here:

https://www.gasandwaterpipelines.co....caAiOHEALw_wcB

Then used a holesaw to make a hole in the wall of the air chamber to glue a 1" pressure pipe elbow for the air supply. If doing this it's worth testing the hole saw on a scrap of pipe first to ensure it's a really snug fit.

Hope that helps.

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Option C would need a swept T to stop you loosing air and flow out the side.

I had a question across the interwebz about being able to use airlifts in the bottom drain. Short answer is yes as it's simply a mechanism that's attempting to push water.

However having essentially two pumps can be complex and lead to overflows (it's better if the return is actually a designed overflow back into the pond for this reason).

So I've put together an example of scenarios that this will work but could pose some issues, there's four scenarios show here to click on the image to resize to see them:

jamie-scenarios.jpg


I've tried to show the natural water level and the risk of overflow in those scenarios (either pond etc).

In Jamie's description he's put the skimmer connecting to the bottom drain part the way up - this can make it difficult to stop the airlift from drawing more from the shallower skimmer than the bottom drain. I'd advise keeping the two seperate and running two airlifts to make balancing the two easier. You can constrain the skimmer line with a joined single airlift but balancing can be a pain and it's not guaranteed to remain balanced if the bottom drain line gets some crud in it. Two lines works better.

Next up is you now have two airlifts providing force and dumping water into the drum tank.Issue here is that is like having a tap always on. In Jamie's design he had a pump pushing water out - that would have to be balanced with the water rate coming in.. which either means a a pump sensor to stop pumping in the event of the water dropping too much which can happen with a drum.

Adding an overflow into the drain works to prevent overflow due to natural rain addition, the danger is the same overflow will work with pumped water overflow ... so the situation means you'd lose water. This is why a drum overflow return into the main pond rather than pump is probably better.. it'll not stop the airlifts pushing water into the drum chamber but they will stop when the back pressure is high enough to counter the force of the airlift. So a higher side drum container.. with a cleanser lower side overflow return is a good.

Remember an air lift is not pumping water.. it's providing force.. if the airlift force overcomes the backward force of water then water flows.. if it doesn't it stops.. which is quite useful to design in (and it won't harm the airlift unlike a blocked pump outlet!).

A bottom drain and airlift could be added inside the pond as a retrofit too however airlifts work best when they're exiting just below the water surface (rather than above the water). The more work the airlift has todo above the water the more back force exists and so the slower the flow.. it very quickly drops to zero flow.

Just be aware that when the drop blocks with dirt before flushing, the clean side will drain and that volume of water will go into the main pond/filter dirty side. So you'll have to calculate the volume of water that will be transferred then how much additional water level height increase the pond/dirty side will increase.

Originally Posted by Hesomable

Hey just got the app it's a lot better I don't mind seeing the 2 pipes in the corner I'm using slip couplers on the main runs I just think if I ever want to change or incorporate airlifts into the bottom drains or change anything I have the option...

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Do not use the slip couplings for airlift pipes, if that is what you mean.
Actually, you could do, if you use sealant and stainless screws. When I added the third air lift, I used one and regretted it.
The slip fittings leak air, it builds up and every 30s you get a massive burp. It is noisy and annoying.
Mark at Cuttlebrook Koi told me he had the same issue.
I've used the solvent weld fittings but they are just slipped in, never had a problem with them.

...just seen this was 5 months ago....