So the working volume of 2.5 rings. Per cubic meter to count simply: V = pr2 * h or 3.14 * 0.75 * 0.75 * 0.9 * 2.5 = 1.59 - get 4 m3. Enough that the water has to be defended. An important caveat - the pipe inside the septic tank tee is better to put that waste water falling down. Since conditionally pure water, which is located in the upper layer is mixed with less dirty.
The bottom of the septic tank concreted. Next, at a distance of 2.5 meters (this is a minimum, preferably at least 3-4 meters) from the septic tank using the same well-known organization of the solar Tajikistan was dug a drainage pit. The depth of the drainage pit 6.7 meters. It is at this depth in this area begins loamy sand, which absorbs water much better than the pure clay, which is located on our depth of 2 to 6.5 meters. But unlike the first excavated hole, the diameter of the second - 1.7 meters, although used exactly the same as concrete ring with a diameter of 1.5 meters. The fact that the sides of the bottom 3 of 7 rings, I poured the gravel, and then made a number of holes perforating a diameter of 6mm.
I assumed that in this case will not only work the bottom, but the walls of the well. This is not some know-how. This is often done by companies specializing in the installation of ready-made VOCs.