Help me design a s/h watering system

[Discus]

I wonder if it might be possible to (fairly cheaply) make a self-starting syphon arrangement out of thin plastic pipe that would result in fairly effective flushing of the pot back down to the level required by SH. Of course, this wouldn't address Ray's concerns over merely diluting the old fluids, but in fish tanks, they say "the solution to pollution is dilution"... So with big enough water volumes, it shouldn't matter too much; more regular flushing == less "stale" solution?

Of course, this does run a significant risk that if the syphon fails (e.g. gets blocked by a root or medium) then your plant root zone goes from SH to submerged, although you could perhaps engineer around this with a very small hole at normal SH hole level.

[Rivka]

Wow that's a good idea for the water in! Really doesn't even needs holes down it sides, just flow out the bottom and someway to stop the leca from pushing up into the pipe. Very doable.

Thinking if I can adjust the flow back and forth a bit the I could get a set up that could fill fast enough without closing the drain. And with the water going in a bit down in the pot, below the top level of leca, it is a lot less likely to disturb it or the plant.
So I can probably skip the drain tube and just let them drain to the trays I am hanging under the shelves. Those will have a drain line coming out of them.