no need for a check valve in a flood sys. Backflow through the pump is a desirable thing in this case as it eliminates the need for any valving.
When the pump shuts off, water just drains backward through the pump.
Ok, now that's just HELL of cool. It reminds me of the Pacific kelp display at the Long Beach Aquarium of the Pacific (used to have a part-time gig there). Those animals need major surge, they use gigantic buckets with these huge pistons that rock them back and forth, and then there's another part of the system that does something a little bit like this gif you put up (which is pretty cool now that I can focus on it). I learned the hard way, any time you can plumb so that you DON'T need to use a check valve, do it that way. In the fish world we call that reservoir a sump, but the sump either acts as a filter or holds filters and the water flow is constant and circular. I don't know enough about either hydroponics or ebb and flow to ask any other questions intelligently, but thanks for that gif, it's wonderful to see things 'in action'.
You, too, could do the plumbing for a public aquarium. Ain't
nothin' like the smell of a fish room, I tell you what.
Yep, that's the bit needed for the overflow, well spotted.
That pic you put back in is the DIY bulkhead that someone adapted from the Durso standpipe overflow. But I don't see why it can't be adapted easily for the ebb and flow.
I dig that gif, I'm saving it to my harddrive.
Cheapest at hardware stores or plumbing supplies, most expensive if you go through an aquarium shop.
I was just as amazed when I first learned how tray-based flood systems work many moons ago. The backflow through the inexpensive centrif pumps makes it happen.