Defining, Understanding Lateral Rehab Options

Part 2 in a series
By Jeff Griffin, Senior Editor | May 2011, Vol. 66 No. 5

Connection Sealing
Brim-Style Main/Lateral Connection Lining -- Brim-style liners typically are installed after the sewer main pipe has had a cured-in-place liner installed. The cured-in-place mainline liner inner’s surface, around the lateral, needs to be properly prepared immediately prior to a brim installation. A resin saturated liner in the shape of a brim or a top hat is positioned on a bladder within the sewer main at the lateral connection allowing the lateral liner to extend into a portion of the lateral pipe. The bladder is inflated pressing the brim against the main and around the lateral opening and the lateral liner is placed tightly against the inside of the lateral pipe. Once the liner is cured the bladder is deflated and removed.

Full-Circle Style Main/Lateral Connection Lining -- This repair is the same as the brim style where a section of the lateral pipe is renewed and the seal is made at the main connection. The full-circle connection liner is structural and can be designed by an engineer to withstand hydrostatic loading.

Installation methods for main/lateral connection lining
The main/lateral lining process rehabilitates both the lateral and the main/lateral connection and always is done from within the main pipe. Lateral and main/lateral connection lining involves one of three installation methods.

Pull-In-Place Method -- A liner assembly of lateral liner tube and either a main brim liner or a full-circle liner is positioned on an inflatable tee-shaped plug which is positioned at the lateral connection from within the main sewer. Then the lateral liner is pulled through the main pipe and up into the lateral via a pull cable that has been previously strung from a clean out to the insertion manhole.

Inversion Method -- Initial steps are similar to the pull-in method with insertion of a liner assembly comprised of a lateral liner tube and a structural or non-structural main connection liner. The main/lateral liner is loaded into a robotic launcher and when positioned at the main/lateral opening, the main liner is inflated against the main pipe and the lateral liner tube is inverted up the lateral pipe. The distance the liner inverts up the lateral is predetermined and can be as little as 6 inches or can be as long as 200 feet. This distance is typically consistent to the length of lateral that is the responsibility of the sewer authority.

Curing methods
Resin systems can be cured in ambient conditions or by heat either as hot water, steam or ultraviolet light.