Septic Tanks
Septic tanks are on-site sewage treatment systems that are often used when a connection to sewage pipes cannot be made. They store substances utilized in sewage industrial processes. Septic tanks consist of two major parts: a septic tank and a drainfield.
Septic tanks are formed using either a molding or welding process. Plastic tank molding, including rotational, blow, and injection molding, involves using a model shape to form the tank. Plastic tank welding is a process in which two pieces of heat-softened plastic are joined through the application of pressure. Examples of this process are hot air and extrusion welding. Septic tanks differ in size and capacity, ranging from small tanks holding a few gallons to tanks exceeding 35 feet in length, with a storage capacity of 50,000 gallons or more.
Septic tanks are formed from a wide variety of plastic materials. Polyethylene (PE), a light, chemical-resistant thermoplastic, is the most commonly used plastic resin. Polyethylene resins can be linear high-density (HDLPE), cross-linked high-density (XLPE), or linear low-density (LLDPE) resins. In comparison, polypropylene (PP) is a light, durable thermoplastic that is denser, stiffer, and stronger than polyethylene and has a high melting point. Polyvinyl chloride (PVC) is a durable, transparent thermoplastic that is resistant to non-essential oils but cannot be exposed to some solvents. Polyvinylidene fluoride (PVDF) is another durable thermoplastic that has high resistance to chemicals and abrasion.