Concrete and plastic are both materials used in the fabrication of septic tanks. Each different type of septic tank offers several advantages as well as disadvantages over the other. For the most part, choosing either type of septic tanks is simply a matter of personal preference.
Plastic septic tanks are watertight and completely resistant to corrosion. They weigh much less than concrete septic tanks making them much easier to install. Concrete septic tanks are very durable and can last for several decades if properly maintained.
Lightweight plastic septic tanks are more likely to be damaged during installation compared to concrete septic tanks. In terms of costs, concrete septic tanks are much more expensive to install and maintain than plastic septic tanks.
Concrete septic tanks have higher effluent levels than plastic septic tanks. Plastic septic tanks are known to "float" to the ground's surface if they are not properly installed. Because of their weight, concrete septic tanks will not "float" to the ground's surface.
Septic tanks made out of concrete are approved for use in every state in America. Plastic septic tanks on the other hand, are not approved for use in all 50 states.
Concrete septic tanks can crack under certain conditions like extreme cold, they also are more prone to leaking than plastic septic tanks. Plastic septic tanks are less susceptible to cracking compared to concrete septic tanks but are by no means completely crack-resistant.