Defining, Understanding Lateral Rehab Options

Part 1 In A Series
By Jeff Griffin, Senior Editor | April 2011 Vol. 66 No. 4

Kiest said a draft of the report was completed in January and distributed to committee members for peer reviews.

“There is an enormous amount of information that needs to be discussed and put into booklet form that is easy to understand and will provide significant education on the benefits of trenchless lateral repairs,” said Kiest. “Once the document is finalized, NASSCO will make it available to association members and the public.”

This article summarizes the content in the draft of the report about the types of resin systems and liner tubes used for rehabilitating laterals. Subsequent articles will cover installation and curing methods, sealing connections and grouting.

Types of lateral rehabilitation
The report identifies six lateral rehabilitation possibilities:

• Lining a section of a lateral;
• Lining the entire lateral;
• Repairing the lateral/main connection;
• Repairing the lateral/main connection and entire lateral by lining;
• Repairing the lateral/main connection by chemical injection; and
• Repairing the lateral/main connection and a portion of or the entire lateral by chemical injection.

All but two of these methods involve cured-in-place pipe technology while the others incorporate chemical or resin injection. Individual lateral pipes often have multiple bends, diameter changes, shifted joints, cracks, deposits and roots, creating a considerable challenge to repair or seal.

Accessibility of the lateral to perform rehabilitation is an issue because one end is located in the sewer main and the other in a building. In some cases a clean-out exists either in the building or outside of the building. Therefore, the report said, it is critical that the rehabilitation methods developed take into account existing conditions in order to provide an effective product and installation method that can be installed efficiently.

Resin systems
Polyester Resin Systems -- Unsaturated polyester resins (UPR) are the workhorse of the CIPP industry and represent approximately 90 percent of resins used. Polyesters are versatile because of their capacity to be modified or tailored during the building of the polymer chains. The principal advantage of these resins is a balance of properties (including mechanical and chemical), dimensional stability, cost and ease of handling or processing.