Precast concrete septic tanks are stronger than tanks made of steel, plastic, fiberglass. When it comes to strength, there's no better choice than precast concrete for your wastewater management system. Stronger than tanks made of steel, plastic, fiberglass, or high-density polyethylene (HDPE), precast concrete septic tanks are known for their superior strength, their durability and their ease of installation--not to mention, they are environmentally friendly, too.