I came here just in the right time to see cool mods like the t-valve technique (thanks @gaiatechnician), and the way of splitting airlift (credits goes to @kenokazaki) allowing two columns to be watered using only one reservoir and airlift.
My window is not tall. I barely have 90cm (roughly 3′). If you already tried to lay out a windowfarm, you already know 30-35cm (1′) is needed per level. On the other hand, choosing small bottles (.5L San Benedetto in my case) allows placing a level in every 19cm (7 1/2″). I have to choose smaller plants, though.
I haven’t wanted to invest a lot, and my first model barely reached $50 mark (10 000 HUF, in the local monopoly game). I bought all plumbing mats from the local aquarium shop, but a day later I decided 4mm ID tubing is not enough: I replaced airlift first, and then all water tubing with 6mm ID. This thicker tubing allows shorter loop (45cm – 1 1/2″), better drip flow, and top airlift splitting works evenly.
I used chains to hang the system, which allows easily place bottles with some string and hand made hooks.
Using small bottles also means you might not want to put net pots into them (however we found small, 55mm – 2 3/16″ diameter ones, they fit nicely), but cutting holes into their bottoms is much easier.
Besides, I’m not a big fan of cutting/drilling big holes into the bottom of bottles. An average DIY person drills three 6mm holes anywhere instead of cutting a single 1″ one to the thickest part of the bottle. My recommendation is this: don’t daisy chain bottles, but let the water flow through an airline pipe. Drill 6mm holes into every bottle bottoms, and drill 5mm holes to each bottle cap. Then, glue 4mm airline tubes into plant bottles’ caps, and a 4mm airline extension connector to the reservoir bottle’s cap. I tried silicone glue too, but I recommend using a glue gun instead.
I started off with spearmint, which filled two bottles. Then I germinated chives seeds in kitchen towel, which now happily sits on top.
Later on I decided to extend my original, more-or-less proof of concept column. However, I ran out of space (putting water next to the radiator is not fun). Fortunately Ken came up with the idea of splitting airlift tube to water two columns at once.
I wanted to try 1.5L bottles too, but keeping the same layout. I ended up cutting bottles in half after painting. Fortunately Jana bottle has a small waist where I can fasten the lace. While I still haven’t wanted to use net pots (for some reason I couldn’t even buy one which fits inside a 1.5L bottle), but I could repurpose some remnants of mosquito net to keep clay pebbles inside.
Small tomatoes, and coriander are placed there already, but strawberries are still too small, I planted germinated seeds to growing pots into coco choir. The lucky ones are expected to be removed to the top of my new column in a week or two.
I also made a video showing how it works.