That’s basically the rise and downfall of a SIP.
Having a system that allows you to not waste water is attractive to us, but it’s not entirely attractive to the plant.
The thing about run-off is that it’s not entirely waste. It’s waste if you have run-off every time, technically, but it also serves to drain what is no longer needed for the plant. I fully intend on going SIP, making the provisions for it right now, but I also fully intend to water them until run-off every 4 to 5 weeks, because the run-off has a service to fulfill to the plant.
The run-off from those times will be recovered and used in the garden outdoors or for my outdoor forest grown plants. Those only get water and the occasional feeding instead of the heavier fed indoor plants and if there are any salt issues they are highly unlikely to pose any issues outdoors where the rain will leach them further out anyway.