Its the other around actually: res must sit lower than grow containers which will allow the water to flow back by way of gravity...otherwise youl need a pump for each container...

Have a look at ebb and flow systems on the web...youll find that the reservoir usually sits under the flood table...

Cheers!

What K says is correct. you can't get a single siphon to work as if one tub drains before the others, it will break the vacuum and the other tubs won't drain.

I am not sure what the diagram represents. The subreservoirs: what is their purpose? If those are the planters, then here is what you do: Set your planters at a higher level. set the blue reservoir at a level lower than the planters. Use an immersible pump in the blue drum to pump the nutrient up to the planters and use passive drainage to let the solution drain back from planters to the drum.

You perhaps should search the net for "hydroponics DIY". that will give you the basics. There is a lot written on the web about it. The pump can be bought at walmart in the fish tank section or at twice the price from Hydroponic stores or very cheap from ebay.

One suggestion, if this is your first time gardening, do soil gardening first, then move on to hydroponics. If you do hydroponics now, do an "ebb & flow" or "fill & drain" system, it is easier and lot more forgiving. In either case, start out real small and experiment. You first season will be just learning. Good luck.

I'm not sure what water pumps they carry in the fish supply's, I only get air pumps in that department/pet stores. I get my water pumps from the nursery department at Lowe's or Home depot. Just look at the fountain and pond pumps. They have many different sizes, and cost well less than hydroponic stores. Not to mention there isn't any shipping costs, or problems with costumer service like some online outlets.

Water does not flow uphill unless you add power.

Is there any reason you just can't lift the tubs and pour it back in. Would be good areation for you fluid. Or...or if you have access to an air pump just use a thin pipe for the return and the air would carry it back. I don't know what it was called but there's some one doing that with on utube.

Agree with most of what people are saying, design it so they drain back into the reservoirs. Something to think about, burying the reservoir so that during the hot summer (and cold winter) the water is cooler than one sitting on the ground absorbing heat. I did it this year and from comments from others it is suppose to help during the long hot days.