Felt Hat

Published: July 31, 2018 | Last updated: July 5, 2023

What Does Felt Hat Mean?

A felt hat is a repair seal installed between the main sewer and a house connection during trenchless pipe relining. This seal is made of inflatable rubber tubing, which holds the felt hat in place during the curing process.

The felt hat is saturated with a polyester or epoxy resin which is cured by ambient air drying, heat or ultraviolet light. The felt hat ensures the structural and watertight integrity of the connection.


Trenchlesspedia Explains Felt Hat

The felt hat is inserted in place by a wheeled crawler robot remotely operated from the surface. The lighting system and camera allow the operators on the surface to insert and tighten the felt hat for each lateral in the portion of the sewer main under repair.

When all laterals have been reconnected to the sewer main and the liner is ready for the curing process, the robot is withdrawn from the sewer main and curing, whether by forced air, ultraviolet radiation or heat commences.


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