My system coming together w/pics
Working at a feverish pace to get my patio greenhouse up and re-start the old gutter airlift hydroponic system! These pics show the inlet/outlet area...inlet is inserted 1" and outlet is 3/4" (both are 1-1/4" dia. pvc pipe). The wrap-around patio 60' of guttering is exactly level so it's a simple matter of airlift nutrient solution being fed through by natural flow of in/out.
What makes an airlift work? The inlet pipe extends to 1-3/4" off the bottom of the old chest freezer. An air stone is extended 3" into the bottom of the inlet pipe. When bubbling, the column of water inside the inlet pipe becomes saturated with bubbles, thus making it lighter than the water in the freezer reservoir that by gravity, tries to constantly fill the "void" in the inlet pipe, forcing the aerated water up and out the inlet pipe. They require no filters since there is nothing to clog and aerate the water being moved.
The General Hydroponics Dual Diaphragm Air Pump provides minimal bubbling/flow (sadly disappointed!) from one outlet at 28" depth of water so I opted to use it for aerating the gutter row and am powering the airlift with an old refrigerator compressor powered by a 1/4hp electric motor. This compressor uses a lubricating oil internally so I built a filter/separator out of a quart mason jar to catch any oil that might bleed through. Don't know the exact gpm flow rate yet but it lifts a good amount of water and will likely have to be toned down a bit! I will lose airlift when reservoir level drops 10 inches so that's approx. 25-30 gallons of use before any refill worries.
Since I have such a long run of guttering, another airline is fed throughout the tail-end 30' or so with an air stone about every 2' to aerate solution which might be otherwise oxygen starved from front section roots.
I had previously posted about making several rows of guttering but opted to make this wrap-around configuration to allow for space in the center of the patio which will get screened in come warm weather. The freezer and gutter rows will be covered to keep light out and plants will be set soon!
Have four varieties of tomato, snap peas, onions, lettuce, spinach, yellow squash and asparagus started in the cups. Some will go out in the dirt, some will go in the hydro system. Haven't decided on a root anchor media yet but have 3" net pots. Big plants will be supported mainly by strings to rafters. I can't wait to get this baby finished! Any comments, critiques and/or suggestions are appreciated.