Category
CIPP
CIPP
CIPP
CIPP
CIPP
Question
NASSCO Response
How many CIPP samples should be tested for a project?
The number of samples depends on the number of MH to MH sections. The inspector typically dictates when tests should be
performed and authorizes payment directly by the owner. The contractor, by contract specified requirement, should provide
a sample for every line section installed.
Apr-15
Why is CIPP water inversion and curing considered to have a 50 year design life?
The long term life of a CIPP is predicted to be 50 years based on a documented installation about 40 years ago. Water is
definitively the oldest curing technique, but more efficient methods such as steam and UV light have been developed and
will achieve the same end result when executed properly. Regardless of the method, the achievement of a fully cured pipe is
what is important.
Apr-15
Are wrinkles/fins in CIPP a problem?
It depends on their location and configuration. Removal of wrinkles or fins is recommended when they exceed a certain
height and are located in the invert and affect the flow characteristics of the pipe or can cause excessive flow backup or
maintenance issues. Wrinkling is often the result of excess of liner material, for instance installing a 15 inch liner into a 12
inch pipe. Wrinkles in the radial (circumferential) direction are typically more critical than the ones in the longitudinal
direction. Radial wrinkles affect the flow characteristics and may allow for debris build‐up in the pipe. Radial wrinkles
located at the pipe invert generally create more issues than the ones located at the pipe crown.
Apr-15
How are wrinkles/fins removed?
Wrinkles or fins can be readily removed on thin liners using a wire brush technique and on thicker liners using a cutting
blade. If the wrinkles or fins have cured in a tight configuration causing the resin to be contiguous in the fin crosssection
then removal of the fin should require no additional repair. If they have not cured in a tight configuration and the resin is not
contiguous across the wrinkle, a short liner repair should be installed where the wrinkles or fins have been removed. If the
repair is extensive the contractor may choose to install a thin liner into the entire section instead of multiple short liner
repairs.
Apr-15
The cool down temperature should be 100 degrees Fahrenheit or cooler whenever possible. A plastic, such as the CIPP liner,
will continue to shrink as it cools down to sewer pipe ambient temperatures. The greater the temperature differential
Why do some publications require the CIPP liner to be cooled to 100 degrees Fahrenheit or lower between the release of the pressure and the ambient sewer temperature, the more shrinkage will occur. It is generally
understood that the cooler the temperature upon the release the tighter the fit of the finished product.
after curing and before relieving the internal pressure?
There are three criteria that dictate the thickness design of a CIPP liner:
Date
Apr-15
What dictates the minimum liner thickness?
1) Structural capabilities of the liner to withstand the design pressures imposed on it. The higher the physical properties, the
thinner the product that will be capable of carrying the load.
2) Minimum thickness that is required for the liner to hold up against erosion and abrasion from the flow in the pipe over
time.
3) Minimum thickness required to have sufficient strength to withstand installation forces, pressures and temperatures The
greater of these three will dictate the thickness installed.
Apr-15
CIPP
How do I become a certified inspector?
You can attend any of a number of scheduled Inspector Training & Certification Programs offered by NASSCO. Simply check
our website for a location near you. If there is no location near you, you can sponsor a training program in your area. Check
the training schedule or email support@nassco.org for details.
Apr-15
CIPP
There are technologies available that can line a lateral from the building to the mainline. Recommended that you read
Is it practical/possible to re‐line a lateral by accessing it from inside the building and terminating it "Overview of Lateral and Main/Lateral Connection Lining and Sealing Technologies" prepared by the NASSCO Lateral
at the mainline?
committee that reviews in detail all of the methods available in the industry for lateral rehabilitation.
CIPP
CIPP
Can air testing be done on a 48 inch rehabilitated pipe?
Typically pipelines larger than 30 inches in diameter are not air tested but visually inspected due to the unsafe high pressure
created while air testing a pipe of this size.
Apr-15
Apr-15
Category
Question
NASSCO Response
How can I measure the CIPP resin volume in the field?
The resin volume can be confirmed during the wet‐out of the liner at the contractor's wet‐out facility. The alternative is to
require that a certified wet‐out report be submitted by the contractor for each liner length to be installed for the project. The
inspector can check the wet‐out report quantities against the contractor's submittals. A trained and certified NASSCO
inspector will learn how to review all contract specified quality control requirements to ensure that the owner's expectations
are achieved by the contractor.
Apr-15
CIPP
Should the specifications require a 400,000 psi resin or higher number than the usual 250,000
psi?
Resin strengths have improved significantly over the years. The 250,000 psi minimum flexural modulus has been in
specifications since the beginning. If a higher strength minimum is specified, then the pipe will calculate out at a thinner
thickness. In all cases, the resin manufacturer should be consulted to determine what resin strength is reasonably achievable
in the field for their resin systems.
Apr-15
CIPP
Can a house connection address be added to a lateral liner for identification purposes?
Yes, there are some systems that will have the address printed on the inside of the mainline section so that it can be
identified with a CCTV camera inspection.
Apr-15
CIPP
I am unfamiliar with CIPP end seals. What is their principle?
End sealing techniques have been used successfully for many years where the liner pipe enters the manhole. The seals are
produced from hydrophilic rubber, which absorbs water and thereby swells to many times its original size, stopping water
from entering the manhole from between the liner and the host pipe. This type of seal has been used to seal construction
joints in a variety of applications including sewer pipe and manhole joints. There are a number of sources, including
Hydrotite from Greanstreak Group Inc., and Insignia from LMK Industries, which has produced a product specifically for liner
applications.
Apr-15
CIPP
There is a section of pipe where the CIPP sample plates were not prepared properly and resin
appears to have leaked out so they are not meeting strength and flex. Is cutting a section out of
the pipe and testing that section an acceptable solution?
Cutting a section of pipe out of the lined pipe is the only alternative. Check with a certified laboratory to determine the size
sample that will need to be cut out and have the Contractor submit a recommended repair procedure from the
manufacturer for the section where the sample was removed.
May-15
CIPP
Date