mojo, NaH2O and others, I definately see the logic behind your thinking and agree with it. However, I'm still a bit concerned with some of the mechanical issues of doing it this way.
OK...worse case scenerio...organics partially clog up part of the coarser mesh. We draw water off the system. Flow through this area is resricted, and the draw compacts more material there. Eventually, this could lead to "dead" spots in the substrate where organics accumulate. In addition, increased diffusion in one area could have a negative effect on the anerobic zone.
I still think that the key to making this system work well will be equal diffusion through the entire substrate into the plenum, and as a "sand junkie", I'd trade letting the substrate reduce as much as possible for for good equal diffusion into the plenum...
MikeS
OK...worse case scenerio...organics partially clog up part of the coarser mesh. We draw water off the system. Flow through this area is resricted, and the draw compacts more material there. Eventually, this could lead to "dead" spots in the substrate where organics accumulate. In addition, increased diffusion in one area could have a negative effect on the anerobic zone.
I still think that the key to making this system work well will be equal diffusion through the entire substrate into the plenum, and as a "sand junkie", I'd trade letting the substrate reduce as much as possible for for good equal diffusion into the plenum...
MikeS