Thread: 2025 is the year for me to move to airlifts…

I’ve really struggled with keeping my pond clear for a while and I think it’s partly because of flow rates and I’ve been turning the UV off because when everything is at full blast I’m using 9.5kWh a day. I’m thinking of changing to an air lift as I think I can get this down to around 3kWh which is very appealing!

Has anyone seen/produced a step by step guide including parts required for building an air lift?

Cheers,

DD

A few of us on here have done it. My whole pond filter runs on two 60lpm air pumps. It could be one, but I use two to max out my flow and have contingency for if one packs up.

There's you tube videos for the "dutch Koi pond method", shall we say, with grey pressure pipe.
Plenty of much cheaper diy methods on there too.

My way is slightly different using sump, with collection chamber, which can then gravity return back to the pond.
You loose a bit of momentum in the water flow, I've found in my method, but you gain the ability to have low returns, rather than just surface returns.

Check out my pond build thread for that. The airlift stuff starts coming together at page 23.

https://www.koiforum.uk/pond-constru...w-pond-23.html

Aim for 1.5m long pipes , but mine work well for me at 90cm, more by luck than judgement, but I'm anoxic and don't need the high flow. So anything in between will work.

Build in 'up' pipes in your returns to avoid bubbles on pond surface and they will also skim off excess proteins when they are present in the pond.

I used push fit soil pipe fittings. Next time I would use solvent weld, or at least run some sealant round and use a couple of stainless grub screws, as every so often some air builds up at the joint and they 'belch' past the seal about twice an hour. Not crucial, just a hindsight thing that mildly irritated me to begin with.

https://www.koiforum.uk/pond-diy-tip...light=Air+lift

As Al said a few on here have done this above is my attempt which works great.
I did a "U" bend one which I found so much easier to do.
My only problem was going through the fiberglass as I sealed round the 4" pipe with ct1 which eventually leaked so now fitted a tank connecter which is much better.
Hardest part was digging the hole next to the pond !!!!

I'd recommend going for an air lift too. I use a hiblow 80xp to run my bio filter and my air lift. And control the flow with a manifold.

It is super cheap to run, no moving parts to get broken (other than in the air pump itself) and it aerates your water.

You have two main options. Either the u bend method that John employed, or a collector method, which is essentially a very tall tank/vessel that you sit the airlift in. Both should work fine if you use 4"/110mm pipework.

The deeper you inject air underwater the more it will expand as it rises. So, as suggested above you want the airlift to be fairly deep (although if you go too deep this may place extra strain on the air pump). When I researched building mine, the advice was to go for air lifts that are 1.5m - 2m tall. In the end I managed to get 1.7m tall. But as above you could probably get away with a shorter one.

Hopefully my drawings give an idea on set up. PXL_20250204_160537918.jpg

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Also there are two main ways to inject air into the bottom of the air lift pipe. Either an air stone that is shoved down the air lift pipe until the air stone touches the bottom.

Or, with a straight connector for a larger diameter pipe plus a couple of clay to plastic rubber boots, you can create a pressure chamber round the air lift, and drill lots of 1mm holes in the air lift pipe where the pressure chamber sits over. By pumping air into the pressure chamber, this will then inject a stream of tiny bubbles all around the pipe at the bottom of the airlift.

When I built mine I did the latter, but with hindsight, just shoving a large air stone down the air lift pipe is much simpler.

What ever option you go for try and have 2 air vent pipes to remove all the foam and bubbles before the water returns back into your pond.

As you can see in the attached, at the top of my air lift I put a swept bend on the top of the airlift before I had the 2 x air vents. I did that to direct the flow of water straight at the pond, but I'm pretty sure it works just as well if you have the air vent directly at the top of the air lift. PXL_20250204_161700784.jpg

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As T white has touched upon the theme. I would be careful about going too deep. T'internet will tell you, you 'need' to be at 1.5m deep at least. As the theory dictates. Trouble is, the theory doesn't account for how much harder your air pump has to work at those depths. Even at 5ft deep compared to 4ft it's a big difference, and exponentially after that. 6ft seems to be that much worse again.
I would think, in reality about 1.2-1.5 would be the sweet spot.

Tbh that was why I went for a hi blow xp pump, due to the depth. They seemed to be a well regarded pump and from what I recall, the depth of the air lift was still within the optimum pressure ranges.

Touch wood, the pump has been working solidly since the pond was up and running in late 2019.

Whereas a cheap jecod/jebao pump on my qt has broken down within about 2 years. And that was only pumping to a depth of about 70cm as well.

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I have an excel spreadsheet that does the calculations for size/depth/airflow to get the required water flow.
It is not my original work, but I put a nicer interface on it.
Happy to share with anyone that wants it.
PM me with your email and I'll send it on.Airlift interface.png

I did a set of diagrams to show working out in the old airlift thread - don't skimp on the air supply (I used 32mm).

If you can use the bottom drain air as a pressure relief valve so there's no valve on it just the water pressure. The lifts will be above that hence it should come out of those first.

If you scroll down far enough you'll get to the airlift: https://www.ukzero.com/pond5M.htm
I use a single 55W air pump for roughly 8 months and a 25W air pump for roughly 4 months (turning down air pumps doesn't really work).
Getting about 17-18,000 litres/hour running 55W pump.