by BK
My Airlift System
12:49 pm in How-Tos, posts with pitcures!, pumps, Water flow by BK
Similar to the other T-Valve Airlift System, I have set up the following. This is probably the best design so far. It has the move water flow and doesn’t suffer the needle valve complexities. Note I still use a check valve on my air flow to protect my pump. It appears crucial that the T-Valve be BELOW the water line otherwise the air just seems to pump into the bottom container. Cheers!! 
Update: 12/18
One thing to note, and this is simple physics! If you are getting bubbles back into your bottom container, simply make the tube labeled “Water” below much longer. Just coil it up below. Simple physics means that the pressure in the Water tube (due to the length and therefore the amount of water) will overcome the pressure of pushing the water up the Air (airlift) tube! Mr Wizard…we thank you!
As you said, I found that tweaking the length of the water tube (with red arrows in your illustration) was crucial to getting the right balance between air and water in the water tube going up to the plants.
Your recommendation of putting the pump BELOW water level is a bit dangerous, as check valves may fail. Sounds theoretical, but happened to me on the first day: It lets small amounts of water flow back into the air tube. Putting the pump ABOVE the water level means you’ve got gravity on your side: Water doesn’t flow upwards unless you apply air pressure TOWARDS the pump, which isn’t the case.
Sorry that my post wasn’t clear, and I agree that the pump shouldn’t be placed below the water line. What I meant was that the T-Valve should be below the water line, not the pump. Thanks for offering clarification Ingo.
hey BK, thanks for sharing this it looks like an elegant design.
let me ask you something, from the image it looks like the tubes are connected in a closed circuity ( the water aren’t dripping into the main water reservoir, mixing together and going up again ).
is that the case?
or i’m missing something in the image and the water coming down into the main reservoir and mixing together?
the reason that i’m asking, if it’s a close system, i think it can make it harder for us to adjust the pH levels since the water aren’t mixing together. the scenario i see in an open system where the water comes down and mix, 1) you can shut off the pumps, 2) wait till all the water is coming down to the reservoir 3) treat the pH level and measure it, knowing it’s the correct measurement for the whole water 4) and turn the pump back on.