What Is a Cured-In-Place Pipe?

A cured-in-place pipe (CIPP) is a pipe that has been repaired by lining its interior with a resin that cures once it is in place. Installation of the liner requires no excavation, so this is sometimes referred to as a trenchless technology. Beyond repairing damage to the pipe, a cured-in-place pipe offers performance, durability, and other benefits.

Repair of a pipe using this non-invasive CIPP technology begins with diagnosis of the problem area. This often involves mapping the pipe system and interior inspection with a camera. Once the problem area is identified, the pipe is cleaned and prepared for installation of the lining. The particular steps involved depend on the type of pipe being repaired, the cause of the damage, and so on. For example, it may be necessary to remove mineral buildup or corrosion or to cut away roots intruding through a break in the pipe.

Once preparation is complete, the pipe can be repaired. No excavation is required to install a cured-in-place pipe. Bypass pumps, hoses, and so on are generally necessary, however, to divert flow around the damaged area while it is repaired. Installation may be done using one of two techniques. A cured-in-place pipe may be pulled into place or it may be installed by the inversion method.

To install a cured-in-place pipe by the pulled-in method, a contractor pulls a resin-saturated fabric tube into place in the damaged area. This is most commonly a felt tube, although other types of fabric tubes may also be used. The tube is inflated to make contact with the pipe walls. Then the resin is cured to form a tight, seamless pipe inside the damaged area. Curing may take place at ambient temperature, with the aid of hot water or steam, or sometimes with exposure to ultraviolet light.

The inversion method involves rolling a liner out from the point of entry into place in the damaged pipe. It is filled with air, water or steam to inflate it against the pipe’s walls. Once it is in place, the liner is cured similarly to the pulled in method. Finally, the ends of the cured-in-place pipe are trimmed and removed.

One advantage of the pulled-in method over the inversion method is that it can be used to line multiple angles. With the pulled-in method, it is also possible to line only a small damaged section instead of the entire pipe. Many contractors offer both methods of installation to their customers.

A variety of resins are available that are suitable for numerous applications. Polyester resins are generally the most economical while offering long life and good chemical resistance. Vinyl resins provide excellent chemical and fatigue resistance, and they perform well in high temperature conditions. These qualities make them highly suitable for industrial applications involving high pressure and temperature conditions and corrosive environments. Epoxy resins can help prevent buildup and blockage in the interior of the pipe because it is difficult for mineral deposits to adhere to epoxy.

Once the cured-in-place is completely installed, the contractor generally inspects and tests the repair to ensure quality and functionality. Leak testing and camera inspection can verify structural quality. A variety of fluid-flow and water quality tests can verify acceptable system functionality.

CIPP trenchless technology offers many benefits to the customer. Since no digging is required, there is no chance to damage other pipes or underground infrastructure nearby. Installation is also much faster and less expensive than traditional repair because it avoids the time and cost of excavation.

While a cured-in-place pipe does reduce the interior diameter of a pipe, it may actually improve flow through the pipe. The resin forms a much smoother surface than the original pipe material, thereby facilitating fluid flow. Its seamless seal also averts many problems commonly associated with pipe joints. Such problems include corrosion, root intrusion, and structural damage at the joints due to minor seismic activity.

Cured-in-place pipe repair may be used in industrial applications such as sanitary or storm sewers or in water mains. This technology is also used in residential applications. Industry standards provide details on proper construction and liner design. Local construction codes may govern this type of repair.