Concrete septic tanks have a number of significant advantages over their plastic or fiberglass counterparts. They have a higher effluent level than the plastic variety; they tend to be tougher, more durable and longer lasting than plastic septic tanks; they rarely experience float; and they are approved for use in all 50 states. Some municipalities mandate the use of concrete for septic systems. Overall, concrete provides exceptional value for the homeowner's money. But there are also some problems with concrete septic tanks.
Concrete septic tanks can be quite expensive to install when compared to plastic septic tanks because their weight (up to 10 tons) will require the use of heavy equipment, perhaps even a crane. Total costs nationwide average $3,000 to $5,000, but can range up to more than $15,000 depending on the municipality, soil, local codes and type of tank.
Concrete septic tanks have been known to crack if a heavy vehicle is driven over them. If the concrete is of an inferior composition it can crack from subtle shifts in the soil. Cracks can result in leaks which can contaminate the surrounding soil and pose a health risk.
Preformed concrete septic tanks are quite heavy, making their transport and installation more of a challenge than comparable plastic tanks. A 500-gallon concrete tank will weigh approximately 8,000 lbs., while a similar plastic tank weighs only 450 lbs.
Concrete septic tanks can be affected by sewer gases which can hasten their deterioration.
Concrete is more susceptible to penetration by tree roots than fiberglass septic tanks.