Ultraviolet fiberglass cured in place pipe (CIPP) liner is far superior in many ways to felt pipe lining.
One of the main reasons to use fiberglass liner with UV curing, instead of water or steam cured felt liners, is that felt curing causes by-products that negatively affect the environment. In particular cities using felt liners are concerned about flushing styrene-laced water into their sewer systems. However UV cured fiberglass pipe lining is environmentally friendly for pipe rehabilitation.
According to a Jan/Feb 2005 article in Stormwater magazine, when a failed storm sewer pipe 18 miles east of Breckenridge, Colorado, was causing a sinkhole underneath I-70 the Colorado Department of Transportation (CDOT) decided to use cured in place felt liner to repair the pipe instead of replace it. They used a polyester felt tube liner, saturated with resin and coated with a waterproof layer which was inserted into the pipe. Hot water or steam was circulated through the tube, which hardened the resin. Because of the styrene-laced by-product of using felt with water or steam curing, the CDOT environmental division directed the liner company to construct a temporary holding pond with an EPDM (ethylene propylene diene monomer) geomembrane liner to capture any styrene-laced cure water. The liner company then had to pump out and haul the water off-site to avoid any environmental contamination. If they had used UV fiberglass cured in place pipe, they would not have had this problem causing additional time and expense to the job.
Another advantage to fiberglass cured in place pipe liner over felt is the curing time. The curing time for felt liners is 2.5 hours but only 50 minutes for a length of 300 feet of 8″ UV CIPP liner. There is also one to two hours cooling time for felt and zero for fiberglass.
If you look at just the curing speed and the effect on the environment, you can already see how UV cured fiberglass liner makes more sense than using felt. But add to that the fact that the fiberglass pipe lining does not shrink (felt shrinks up to 13%, requiring residual grouting and lateral seals) and it has a minimum life span of 50 years, you really see how using fiberglass CIPP liner is the right choice.