The rock system is the most common type of septic system available (septic installers are very familiar with this system). The rock and pipe system operates very easily; the effluent leaves the home to the septic tank where it receives pre-treatment and moves to the first distribution box (if non-pumped system). If the system is an equal flow distribution type then the effluent will go to all the lines at one time spreading the effluent over the entire field allowing for faster absorption. If the system is a hillside distribution type, then the effluent will go to the first box and then the first line. Once the first line fills to the maximum level the effluent will move to the next box and the next line. This will continue until the end of the lines or the effluent is absorbed.