The ASD PCK 1.5 – 4 S biological treatment plant is the second most popular model of the treatment plant produced by the company. This sewage treatment plant differs from the standard treatment plant ASD PCK 1.5 – 4 in that it is shortened by 30 cm. As a result, the treatment plant can be buried in high groundwater, as well as where the outgoing pipe leaves the house relatively shallow. These shortened devices are chosen by all owners of private houses, whose number of users starts from 2 people and does not exceed 6 inhabitants at full load, also these devices can be used by the residents of summer houses, connected to saunas.