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Frequently Asked Questions

What Is Cured-In-Place Pipe (CIPP)?

CIPP is a means of rehabilitating an existing water main using a woven polyester tube that is impregnated with liquid resin. The resin is hardened through the application of heat. Once the resin has cured it becomes a structural component which lines the internal dimensions of an existing sewer pipe, taking the form of the pipe’s interior and shape. The CIPP liner is composed of two concentric tubular plain sleeves. Its inner sleeve is coated with polyurethane, and both sleeves consist of woven polyester.

What are the various applications for CIPP?

CIPP can be used to structurally reline damaged sewer and water mains. CIPP can be used to overcome poor hydraulic performance, eliminate frequent breaks, and eliminate inflow and infiltration to existing utility mains.

What is water main swabbing?

A polyurethane foam swab is propelled through a new water main through the use of water pressure.
Swabbing is used in the commissioning of new water mains. Swabbing removes all debris within the new water main that has accumulated during construction.

What is CCTV?

CCTV (Closed Circuit Television) consists of a robot-crawler mounted camera that is connected to a monitor by a power and video transmission cable. CCTV is used to perform and record visual inspections of the inside of mains to determine the extent of main deterioration, the placement of service lateral plugging caps, and the removal of service laterals.

The CCTV video is captured onto a DVD disk for further inspection and archiving. The information contained on the disk can be analyzed at any time to determine the extent of the required rehabilitation. The information is also used for lifecycle management planning and justification for the allocation of maintenance funding.

By inserting a CIPP structural liner in a pipe, how much is the hydraulic capacity reduced?  For example, in a 900mm CSP culvert? 

Installing a CIPP liner does not reduce the hydraulic capacity of the pipe.  Although the diameter is reduced slightly, as a minimum, the pipe’s hydraulic capacity following the CIPP rehabilitation meets 100% of the existing pipe’s hydraulic capacity according to ASTM F1216 “Standard Practice for Rehabilitation of Existing Pipelines and Conduits by the Inversion and Curing of a Resin-Impregnated Tube.”  This can be verified by referring to Manning’s equation for gravity flow.  Because of its smooth finish, a CIPP liner has a Manning’s coefficient of 0.010 compared to 0.012 for a concrete pipe and 0.022 for a CSP pipe.  As a general rule, the CIPP liner is designed to reinstate the structural capacities of the pipe while also increasing the hydraulic capacity.

Taking a 900mm (36”) diameter CSP culvert as an example, assuming a 1% slope, a 21mm thick liner, and comparing results for a water depth of 9 inches in the pipe, the calculated hydraulic capacity after the installation of the CIPP liner is 326L/s compared to 153L/s before the rehabilitation.  The hydraulic capacity of the pipe after lining is more than double the existing CSP culvert’s hydraulic capacity even with a diameter reduction equivalent to 95.4%.  Also, the maximum capacity of the relined culvert is calculated at 2330L/s compared to 1200L/s before the rehabilitation with Manning’s equation.  Calculated results of the hydraulic capacity are expressed in the chart below as a function of the water depth in the culvert.   (Answer and calculations by Nicolas Brennan, B.A.Sc., Estimator and Project Manager at CWW)