This is my 2 liter ebb and flow or flood and drain hydroponics setup. Total parts cost maybe -80. I used an old entertainment center that I was about to toss. I cut holes in the shelf to recieve the tops of each of the 2 liter bottles, cut the bottoms off the bottles and inverted them. The fittings I first tried to JB Weld nylon hose barbs into holes drilled in the caps and they almost all failed. My revision was to instead use some cheap corks, drill holes in them and gorrilla glue some PEX tubing pieces into them, then wrap some plumbers/thread tape around the other end of each PEX piece, insert that into the tubing and then double wrap it with zip ties. This ends up being water tight and no leaks. The timer turns the air pump on for 15 min. every six hours and the air pushes the nutrient water down and up the tube into the distribution manifold to each grow chamber. That little green valve in the air line by the pump allows me to adjust how fast the air is released from the nutrient water chamber and thus how fast the grow chambers drain out via gravity. The air valve of course can’t be wide open otherwise the tiny little air pump can’t build the pressure needed to lift the water. If the release valve is all the way closed, the flood happens faster, but it takes too long to drain out and the water just sits in the grow chambers. The grow media is just pea gravel inside a foodsaver bag cut from a roll with pin holes poked into it with a sewing machine. The bag then acts as a sieve and water flows freely in and out of it.