My Aquifer > Septic System Basics > What is the best kind of tank to use?
Concrete tanks are the best. They are durable, corrosion-resistant and have proved effective over the long-term.
Fiberglass tanks are relatively new and may be equally as effective, however no long-term data is available yet. Also, there is the possibility of damage occurring to the fiberglass during transport and placement of the tank.
Steel tanks eventually rust. A life expectancy of 30 years is not unreasonable, although this varies with the moisture and acidity levels of the soil. Steel tanks usually rust first above the water line because of the greater oxygen content in the unsaturated zone (iron + oxygen + moisture = rust).