Inversion lining is a method of lining a host pipe. It is the process of turning a coated fabric tube inside out with water or air pressure, like a sock rolling out inside the pipe. Inversion is often used for large diameter long main line (sewer) runs. Inversion is also used when there is only one access point.
Inversion lining is a multi-part process. Once the liner has been blown in place, it flattens and folds in on itself. To resolve this, a calibration tube is then blown through the inside diameter of the liner and inflated to expand the liner and force it to conform to the shape of the host pipe.
Many house laterals transition from four inch to six inch. Transitions between pipe sizes can present a challenge using inversion systems. One method of handling this is to stitch a transition liner in place, located according to measurements taken. Sometimes, excess materials in stitched liner sections will create a lip inside the pipe.
Another method of lining transitions is the use of “stretch” liners but that requires precise positioning because stretching in one end will cause shrinkage in the other. It does also sometimes happen with inversion methods of relining that the measurements can be thrown off by the liner stretching with the pressure being used to blow it in place.
These problems are completely eliminated with the Formadrain lining system. Formadrain liners conform to the shape and size of the host pipe, flawlessly transitioning different pipe sizes without the need for “stretch” liners or stitching sections together.
With an inversion system, lateral-main and other connections must be reinstated mechanically. That is also an option with the Formadrain system but, unlike inversion systems, gapping a Formadrain liner is easy to do.
Formadrain also offers The Formadrain LMC (lateral-main-connection) to provide a watertight connection and without sacrificing structural strength.
Curing the Liner
There are different methods of curing a liner placed using inversion, including steam, hot water, and air, or a combination. Because the resins that are used in the inversion systems were not designed for steam, the steam is applied for only ten minutes or so. It is disconnected after that because the steam, if applied any longer than that, would cause the liner to boil and blister. After the steam is discontinued, it becomes an ambient cure and the amount of time it takes to thoroughly cure is generally a matter of guesswork.
The epoxy used in Formadrain liners is specifically designed for steam curing. Complete and certain curing of a Formadrain liner takes place in as little as 45 minutes.
Many inversion systems use a styrene-based solvent polyester and there is growing concern that styrene may be carcinogenic. Formadrain’s resins are non-toxic and VOC free.
To find out more about how to become a Formadrain licensee, contact Bruce Stevenson, Business Development Manager, at 1-888-337-6764 or Bruce@formadrain.com.