I had been chatting via email with a friend in Australia for a few days. His hobby is designing and building hydrofoil surfcraft (for the past 20 years). I mentioned I was working on developing an airlift pump project.
He was very interested in airlift pump technology and wanted to test it in a 5,000 liter “plunge pool” that he just installed. He came up with a simple, off-the-shelf item to make a small prototype rectangular airlift riser for testing purposes – a 3”x4”, plastic downspout.
I calculated he would need about 1.7 cfm airflow injected at 30” (100% airlift submergence) using a 1/2"-3/4" inner diameter (ID) horizontal injector cylinder. The water pumping rate should be 70% higher than a single 3” ID airlift (@ 1.0 cfm air) and the same or slightly more than a single 4” ID airlift (@ 2.0 cfm air).
(Looks like 3”x4”, rectangular vinyl downspouts are available at Lowes in 10’ lengths.)
I came up with a compact horizontal injector configuration for a 3"x4" downspout riser (picture below). This injector would be connected to two (2), 1/2" ID air delivery lines branching off a 3/4" ID line.
I used 3/4" npt x 1/2" barbs; 3/4" 90 elbows, S x FPT, Sch. 40 PVC; and 3/4" SDR-21 (thin-wall) PVC pipe.
The 3/4” SDR-21 PVC pipe provides more ID than Schedule 40 pipe, for low resistance air flow.
I used 3/4" npt x 1/2" barbs; 3/4" 90 elbows, S x FPT, Sch. 40 PVC; and 3/4" SDR-21 (thin-wall) PVC pipe.
The 3/4” SDR-21 PVC pipe provides more ID than Schedule 40 pipe, for low resistance air flow.
[The same could be done with 1/2" PVC pipe and fittings (last picture).]
Click the following links for:
3" x 4" Vinyl Downspout
Alternate 1/2" ID horizontal injector configuration requiring 3/4" ID air delivery line.
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