Orenco’s Injection-Molded Fiberglass Tanks Set New Industry Standard

Sutherlin, Ore., May 13, 2004 — Since Orenco Systems, Inc., introduced its injection-molded fiberglass tanks in late 2003, nearly 1,000 have been installed, and the tanks have won praise from installers and regulators around the country. Clermont and Hamilton Counties, Ohio, and Bethel Heights, Arkansas, are two places where Orenco’s injection-molded tanks have solved problems — in individual installations in the former case, and in a STEP system in the latter.

In 2002, Clermont and Hamilton Counties began to require septic tanks that were installed as part of dosed systems to be tested during installation for watertightness. The counties adopted this requirement to eliminate problems caused by infiltration. “I think 30–40% of other tanks are failing the watertightness test,” said Conall Stapleton of Onsite Advantage LLC in New Richmond, Ohio, past president of the Ohio Onsite Wastewater Association and an Orenco distributor. “We’ve got 60 molded fiberglass tanks out there, and if there’s a problem, we don’t have to sit and second-guess whether the tank is leaking.”

In Arkansas, the city of Bethel Heights took a different approach to ensuring watertightness when it built a septic tank effluent pump (STEP) system to serve 200 new homes. Seeking to minimize maintenance costs associated with infiltration of water into tanks, the city council passed an ordinance in 2003 mandating that only fiberglass tanks be connected to the system. So far every residential tank installed has been an Orenco tank, and none has failed. Based on the past performance of other kinds of tanks in household systems in that area, “I think we would have had failures,” explained Bethel Heights mayor Fred Jack, a licensed wastewater operator.

Septic tanks must be watertight to keep untreated wastes from leaking out (exfiltration) and to keep groundwater and surface water from leaking in (infiltration). Exfiltration causes environmental damage, increased pumping frequency, and higher maintenance for any in-tank filtering equipment, and can create a public health hazard. Infiltration upsets the settling process and causes solids to be washed out of the tank; the excess water and solids can overwhelm or destroy downstream treatment components and soil dispersal areas. Although most jurisdictions now require tanks to be waterproof and structurally sound, very few require actual testing to prove it. Likewise, very few manufacturers have satisfactorily addressed the problem of making septic tanks watertight and structurally adequate.

In response to these problems, Orenco developed fiberglass-reinforced polyester (FRP) tanks made by an injection-molding process called resin transfer molding (RTM). This process produces perfectly uniform tank halves that are easily assembled into lightweight, yet strong, watertight tanks.

The company distributes the tanks through a network of trained assemblers. After building each tank, Orenco’s tank assemblers test it for watertightness by setting it up above ground, unsupported, and filling it with water. Orenco also requires installers to test every tank for watertightness once the tank is in the hole.

In addition to watertightness testing, vacuum testing is used to assess a tank’s ability to withstand the forces that will act on it in use. A vacuum of approximately 6.5 in. Hg simulates the forces on an empty tank buried four feet deep with water to grade and a 2,500-lb wheel load. Orenco’s 1,000-gallon tanks can withstand a vacuum of 13 to 14 in. Hg, and the 1,500-gallon tanks can withstand 11 to 13 in. Hg.

Besides watertightness and strength, Orenco tanks offer several other benefits to the installer and the property owner. The tanks are lightweight, and an assembled tank can be transported in a pickup truck or on a utility trailer. A baffle can be installed in any of a tank’s ribs, allowing designers flexibility in specifying the size of a tank’s two compartments. And because the tanks can accommodate various risers, pump vaults, effluent filters, and pumps, they are suitable for use in many kinds of decentralized wastewater treatment systems.

In fact, Orenco’s ability to supply strong, watertight tanks opens up new possibilities for designers planning such systems. In many areas, tank failures have caused regulators to skeptically view not only traditional septic tank installations but also innovative decentralized systems that depend on septic tanks for primary treatment. “If local or national standards required tanks to be watertight and to pass strength tests, and enforced those requirements, onsite and decentralized systems would be accepted more widely than they are,” said Eric Ball, Orenco’s vice president of product development.

Orenco Systems, Inc. has been designing, manufacturing, and selling products for decentralized wastewater collection and treatment since 1981. The company now employs about 225 people and distributes its products throughout the United States, Canada, New Zealand, and parts of Europe and South America.