A singled zoned timer would feed all the tubs in the same amount of water, wasting a fair amount. With the heavy drinkers were getting their fill and the lighter ones spitting water out of their reservoirs and on to the roof. On hot days some tubs were drinking several gallons of water while others took next to nothing.
Would a zoned timer system be flexible enough to adjust to a yearly "crop" rotation?
I only know the basics of how irrigation systems work. They seem more complicated than the siphon. I'd like to do what ever is easiest/cheapest.
I suppose it depends on whether you want/need full automation or not. I have the feeling that the siphon solution is going to be a pain to keep primed. Maybe if you grouped tubs and linked them so all the tubs in a group had a common water level? I use a gravity fed system to keep the greenhouse and beds watered on a timer from a rainwater barrel, but I don't expect total automation - I tweak the output as I go and supplement where necessary.
Most irrigation systems will allow you adjust the output from each nozzle independently.
