Lateral-to-main connections can be major sources of sewer system infiltration. Even after cured-in-place pipe (CIPP) lining, that junction can remain a significant leak point, in part defeating the purpose of the repair.

Sealing the lateral-to-main connection, whether as a spot repair or after lining and lateral reinstatement, has been a substantial technical challenge. The goal is to create a complete, lasting and leak-free connection that eliminates clear-water entry.

Manufacturers have developed a variety of materials and techniques for sealing the junction. Here are three widely used approaches to creating sound lateral-to-main connections.

Ready templates

The InnerSeal lateral connection from Perma-Liner Industries Inc. is a CIPP resin-impregnated lining system composed of 100 percent solids epoxy. “The product uses scrim-reinforced, non-woven felt with a PVC coating that’s very flexible and impregnated with two-part epoxy,” says Jerry D’Hulster, company president.

The product contains no styrene and as such does not shrink, enabling complete adhesion to the host pipes, he says. Before installation, the pipe is cleared of grease and debris. Using a turnkey trailer system, operators insert premanufactured structural liners designed for lateral connections at 22 degrees, 45 degrees or 90 degrees.

“We have the templates on hand for each type of lateral and can quickly make them to the angle of the existing connection,” says D’Hulster. “Once the camera videotapes the existing pipelines, we can assemble custom-made repair kits the same day and have them in the contractor’s hands within 48 hours.”

The kits are placed from within the mainline and launched into the lateral, creating a watertight seal at the lateral connection. The operator controls the direction of the repair train and positions the train into the lateral connection, where the liner is inverted through the application of air pressure.

The operator controls the inversion pressure to secure the resin-impregnated liner properly against the host pipes. Constant pressure is applied as the liner extends through the lateral, sealing off water infiltration during application.

“The repair places a 4-inch brim inside the main around the lateral connection, then provides a liner for the lateral as well,” says D’Hulster. “We can easily go 50 feet or more up the lateral to seal it against leaks and root intrusion. When you’ve got 300 feet of sewer main with 20 houses along it, each with 75 feet of lateral, almost all of your inflow and infiltration is coming from those laterals, and our product addresses that.”

The resin is ambient-cured, and the formula can be modified for hot-water or steam curing. The product can rehabilitate mains from 6 to 24 inches and laterals from 3 to 8 inches. A crew can complete three to four installs per day.

D’Hulster notes that the InnerSeal system exceeds the specifications of ASTM F 1216: Standard Practice for Rehabilitation of Existing Pipelines and Conduits by the Inversion and Curing of a Resin-Impregnated Tube and has a guaranteed minimum life of 50 years. 866/336-2568; www.perma-liner.com.

Compressive seal

The T-Liner system from LMK Enterprises Inc. is a stand-alone CIPP liner that renews the main-to-lateral connection while also rehabilitating the lateral pipe.

“Our system is not based on adhesion, but on compressive strength while using gasket sealing technology,” says Rick Gage, national sales director. “It is designed to renew the connection while reducing I&I and eliminating root intrusion.

“We start with a coated flat sheet, and on each end we sew a 1-inch strip of compressible material,” Gage says. “Once cured, the one-inch strips provide a smooth transition for flow from upstream to downstream in the mainline pipe. On the other side, we sew a strip of material that provides a smooth transitional overlap.”

The lateral lining, whether it is a T or Y, is centered as one piece to the flat sheet using a sewn and heat-welded tape seam. The lateral lining consists of either coated felt or coated non-woven material, depending on the configuration of the lateral pipe.

“We may use non-woven materials to negotiate bends because they’re more flexible and have more stretch versus the traditional coated felt,” says Gage. Installers catalyze the liner resin and vacuum-impregnate the liner/bladder assembly onsite. The lateral lining is pulled inside a protective sleeve while the mainline portion is wrapped around the launching device, and then the assembly is inserted into the main through a manhole and pulled to the lateral connection.

The liner is robotically positioned at the main-to-lateral interface, and then air pressure is applied. The mainline portion inflates, and then the lateral lining is inverted up the lateral pipe. “Once the lateral connection is positioned, the mainline sheet inflates, embedding the hydrophilic O-rings against the inner wall, producing a 360-degree connection in the main,” says Gage.

“The lateral liner can be extended to just about any length. We’ve inverted as far up as 200 feet from the main.” After the inversion, 20 minutes of steam expedites curing, followed by a 10-minute cool-down. Each repair includes a printed indicia recording the street address, installer name and LMK manufacturing codes that provide information on the coating, and on the liner material, density and lot number that can be later read through a mainline camera.

The manufacturer says the T-Liner system is fully compliant with ASTM F2561-06, Standard Practice for Rehabilitation of a Sewer Service Lateral and Its Connection to the Main Using a One Piece Main and Lateral Cured-in-Place Liner. 815/433-1275; www.performanceliner.com.

Stovepipe hat

The Top Seal from AMerik Engineering is a resin-impregnated, non-woven, enhanced corrosion-resistant fiberglass composite laminate coated with bonding epoxy on the pipe contact surface.

“The product gets its name from its design,” says Erik Nielsen, president. “The seal is shaped like a stovepipe top hat, without the top.” The 6-inch stovepipe portion is sized for the interior circumference of the sewer lateral, and the 3-inch-wide brim seals to the interior surface of the main.

“We don’t go 1 or 2 feet into the lateral,” says Nielsen. “If you need that, you’re probably looking for more than a sealer between the main and the lateral. It doesn’t change the potential for groundwater infiltration or roots, which is better dealt with by a liner extended from the customer side of the lateral.”

The product is assembled in a trailer, placed on a tractor-applicator, then placed in the manhole, delivered to the lateral connection and positioned using the tractor-applicator and TV camera. The stovepipe portion of the composite is inserted into the lateral connection, while the brim remains in the sewer main and forms a reinforcing and sealing ring around the lateral opening.

Once inserted, a bladder is inflated, deploying the seal and pressing the fiberglass containing the epoxy bonding component against the inside of the lateral and main walls ringing the lateral. The inflation of the bladder further presses the laminate into the connection joint, mechanically locking it into position.

Because the laminate is non-woven, the material expands tightly against the pipe walls, taking the shape of the connection.The expandable bladder is longer than the composite, so composite ends taper smoothly to interior pipe surfaces. The system can form to lateral T, Y or break-in connections, bridging smaller voids and cracks.

“Once the side bladder is inserted into the lateral, the operator switches to a second TV camera, placed inside the bladder, to confirm correct placement,” says Nielsen. “The bladder can be deflated to allow the laminate to be adjusted to achieve optimal placement.

“The operator then re-inflates the bladder and activates an ultraviolet light source within the bladder, curing the fiberglass to a solid structure in about seven minutes,” he says. The applicator is cooled for a few minutes, then removed, and the installation is examined using an external camera. Processing time for 8- to 21-inch mains with 4- or 6-inch laterals is about 30 to 45 minutes per installation, working from the same manhole. 770/924-2899; http://amerikengineering.com.