How they differ
A septic tank is a settling tank where wastewater clarifies and then moves on to infiltration or a collection solution. A biological treatment plant actively treats the water and needs electricity and a stable load.
A septic tank is simpler and less sensitive to interruptions, but requires suitable soil and enough space. A biological treatment plant gives a cleaner output but requires regular maintenance and more even use.
What to clarify before deciding
- how many people live in the house permanently
- whether the house is used year-round or seasonally
- what the soil and groundwater level are like
- how much space is available on the plot and where existing lines run
- how access for a septic tanker truck is ensured
What installation involves
Installation means excavation work, setting the pipework's slopes, and connecting to the house's outlet. The scope of work is affected by excavation depth, soil, and the distance from the house to the solution.
The maintenance that comes with the solution
A septic tank needs the sediment layer removed by a tanker truck and the infiltration system's condition monitored. If the infiltration no longer absorbs water, the soil and the structural part of the solution need attention, not just emptying the tank.
A biological treatment plant requires regular maintenance, an electricity supply, and a relatively even load. A long empty period or a sudden change in load affects the treatment process, so this is worth considering separately for a seasonal house.
Common mistakes when choosing
- the solution is chosen without clarifying the soil and groundwater level
- access for the tanker truck is left unplanned
- the location of existing lines only becomes clear during excavation
- the house's outlet slope doesn't match the chosen solution's depth
What work comes with installation
- excavation work and preparation of the ground under the tank
- connecting the inlet and outlet pipework with the correct slope
- for a biological treatment plant, running and connecting the electricity supply
- building the infiltration system or collection solution
- restoring the plot after excavation
Frequently asked questions
- Can an existing septic tank be converted into a biological treatment plant?
- In some cases the existing tank can be used as part of the solution, but it depends on the tank's condition, volume and layout. The decision can only be made after an on-site inspection.
- What affects the scope of installation work the most?
- Excavation depth, soil type, the distance from the house to the solution, and the location of existing lines. These become clear during the plot inspection.