Floating and removable material is extracted from domestic wastewater in mechanical septic tanks.
This is pure mechanical cleaning, for which you need 500 litres of capacity per inhabitant. If you assume a volume of 150 litres, the wastewater passes through the system in three days. These septic tanks must have a total volume of at least 2,000 litres. A 2,000 litre system is sufficient for four inhabitants, another 500 litres, must be incorporated for each additional inhabitant.
| Volume (I) | Length (mm) | Width (mm) | Height (mm) | Weight (kg) |
| 2700 | 2080 | 1565 | 2010 | 120 |
| 3750 | 2280 | 1755 | 2200 | 150 |
| 4850 | 2280 | 1985 | 2430 | 185 |
| 6500 | 2390 | 2190 | 2710 | 220 |
