7:33 pm in Being a good member of this community, Education, Getting Started, Help the project by testing this, How-Tos, International, Materials and Resources, pumps, questions, R&D-I-Y, Uncategorized, Water flow by Brian White
Windowfarms recommend a 4 outlet pump but many people already have a 1 outlet pump and probably would like to use the one they have. So here I have a video about a method to split the air stream to work 2 or more columns. If you just split the air with a Y or T splitter (even if both airlift tubes are exactly the same), the air will “choose” one tube (or the other one) and then all or most of the air will go up that one with zero or almost zero airlift happening in the other one. This is because the “starting pressure” is higher than the “running pressure” for any airlift pump. So whichever one starts first will probably stay running really well at the expense of the second one (which will be either really slow or not running at all!)
The method I show to prevent this is to throttle both of them. In the video, I use little “taps” to tighten and restrict the airflow to both sides until both sides run. AND stay running! For this to work, both airlifts should have similar submergence (but they do not need to go to the same height). You might also be able to see from the video that you can have one going a bit faster than the other. So possibly, you can supply more water to some plants when they are big while in the other airlift supplying just a little to them because they are tinier.
There are other methods too but this one should be easy to do and to adjust.
I only did 2 columns because I didn’t have enough tubing to show 3 working.
3 columns might work in my case (my pump is an old aquarium pump that I found dumped on the side of the road so it is probably not such a good model)
Update 2nd Jan 2012. 3 columns works too but in the case of my pump it is the limit. Video Jan 3 2012. 3 airlift tubes working from a one outlet aquarium bubble pump
Youtube now allows you to edit videos so if I am not too busy, I will “upgrade” the video (and this post) over the next week or 2 and show methods to measure the flow or at least compare flows under different conditions too. Brian