I tried to add a video, but it was invalid so here's the link. Please excuse the music. Youtube wouldn't let me use the original choice, so this is what Youtube picked. It's actually not bad.

Skeetagator on Youtube

This is the love child of two other instructables. The Even Simpler Flood and Drain System - The Mosquito and the Modular Hydroponics - Low Profile Reservoir. Using Gatorade bottles and soft tubing to form a pressure seal, I was finally able to get air and water tight seals between the planters and the drain pipe, sooooooo ....

The unit that I built here is only 19" long, but it should be able to be implemented on a much larger scale easily. As the pipe increases in length, the required volume of air will increase, but not the required pressure. Redundant, individual air pumps would provide the required air, keeping the fill cycle reasonably short, while also providing security against pump failure.

Please also excuse the photos. This was built and tested, rebuilt and tested, rebuilt .........., so the photos describing the steps are of a disassembled, finished unit. My apologies, but it does show how each planter and the reservoir are still separate "modules?", however loosely.

Step 1: What You Need

1 ea Length of 4" diameter drainage pipe. I used a 19" length of 4" PVC.
2 ea 2L Pop Bottles w/caps(NOT Pepsi)
Gatorade bottles w/caps as req'd
7/16" OD clear Vinyl tubing as req'd (4.75 inches per Gatorade bottle)
1/4" Aquarium air tube as required
1 ea small, self tapping screw

Drill
1/2" Drill bit
1/16" Drill bit
13/64" Drill bit
Hot melt glue gun w/glue
Heat gun
Utility knife
Long pry bar thin enough to fit though the neck of a 2L bottle

Step 2: Reservoir

1. Cut drainage pipe to length.
2. In a straight line, on what will be the top of the reservoir, measure and mark the location of the holes for the planters. I used 4.5 inch centers.
3. Drill 1/2 inch holes for each planter. Take care to drill as straight as possible, for proper planter alignment later. Smooth away any burrs or they will cut into the Vinyl tubing later.
4. Bevel the ends of the pipe at approx. 45 degrees.
5. Apply a generous amount of glue to the bevels at each end of the pipe, around the full circumference, being careful not to increase the diameter of the pipe. Allow to cool fully.
6. Cut the top half off one of the bottles and insert over one end of the tube as far as it will go.
7. Cut the bottom off the other 2L bottle and insert the upper piece over the other end of the tube about 2 inches.

STEPS 8 AND 9 MUST BE DONE QUICKLY IN A VERY WELL VENTILATED AREA DUE TO TOXIC OFF-GASSING FROM HEATED PVC AND OTHER PLASTICS

8. Heat the clear plastic dome of the bottle from step 6 so that it shrinks tightly around the pipe, melts the glue and tightens over the end of the pipe. Be careful not to overheat the clear plastic or damage the threaded area with the heat AND heat the PVC pipe AS LITTLE AS POSSIBLE.

9. Heat the clear plastic from step 7 so that it tightens firmly around the pipe and then, using the pry bar and heat gun, shape the neck so that it faces up as in step 4 of Modular Hydroponics - Low Profile Reservoir.

10. Trim excess plastic away from tube using a utility knife.

Note - Both ends could be facing up, but it's only necessary for one. The other end is also the cap end of a bottle, rather than the bottom, because provides access into the tube.

Step 3: Skeetagators

Sorry for the name, but "this" design is Gatorade specific. This is the Mosquito referred to in the introduction, slightly modified to create an easily removable, reusable, seal with the curved surface of the reservoir.

1. Remove the green, turny, valve thingy from the cap of the Gatorade bottle. It will pop right off with a little force, exposing the nozzle.

2. Stretch one end of the 7/16" inch Vinyl tubing with needle nose pliers and slip/force/wrestle it onto the nozzle as far as possible. It must extend past the part where the nozzle gets thick again. This "valley" under the tubing is what will help form a good pressure seal.

3. Repeat as necessary.

Step 4: Air Control Cap

1. Screw 13/64" hole and 1/16" hole into one of the caps.

2. Tap the 1/16" hole with the self tapping screw. The angular notch in the threads of the screw forms a variable air vent when adjusted.

3. Insert the tip of the air hose through the 13/64" hole.

Step 5: Assembly

1. Remove the bottle and feed the tube into the 1/2" hole. Force the Vinyl covered nozzle into the hole as far as it will go. Spinning may make this easier. It WILL stop at the point where the neck of the nozzle expands again.

2. I drilled a vent at this point, for test purposes only, in the bottom of each Gatorade bottle, but to make a planter, simply cut the bottom off and fill with grow medium.

3. Screw on bottles, line them up as best as possible and leave to rest while the vinyl finishes reshaping itself.

4. Cap the ends of the tube, with the "Air Control Cap" going on the upright turned end.

Attach air hose to pump. Fill tube with just enough nutrient, through planters. Test.

Any unused planter holes can be plugged as required.