What flash through was this loop siphon, with a ping pong ball on a stand pipe to aids in cutting off the outflow, as sketch below. Please do let me know if anyone has done this before (with proof of course) for me to give credit. But so far I had search and it return nothing.
A better diagram below on how the siphon is to be constructed. Slight changes needed once build since this sketches and diagram is just the theoretical part.
I did build this siphon and experimented with it earlier today and the video as below. Its still in its infancy with me, I hope to fine tune it so that it will work.
One problem I found is the ball is too light, I may need to look for a heavier ball but still float. Outlet seating for ball too may need some adjustment to make it flat and probably cupping the ball.
A recess below the growbed to accommodate ball is also one possibility to make it work better.
This could be a blunder .. :(