Septic Tank Advice
How long do septic tanks last?
A modern septic tank system (which includes the soakaway), properly used and maintained, can last for anything between 20 and 30 years.
Factors affecting longevity include the permeability of the sub-soil, the type and construction of the septic tank, and the regularity of de-sludging. Porous sub-soils such as gravels will make a soakaway system work more effectively (and hence last longer) than a less porous sub-soil (such as clay).