CIPP liner testing happens after the liner cures, mainly in two ways. A camera is run through the full length to check for wrinkles, pinholes, dry spots and properly reopened branch lines. On city sewer contracts, a cured sample also goes to an independent lab for strength and thickness tests under ASTM F1216.
On a home sewer line, the camera run is the test you can see. The NASSCO CIPP specification calls for the liner to be cleaned, then filmed end to end after branches are reopened. The footage should show no dry spots, pinholes, major wrinkles or separating layers, with each branch reopened to 90 to 95 percent of its original area. A sewer camera inspection before and after lining lets you compare.
Lab tests measure what a camera cannot. NASSCO’s guideline sets minimums for a sample cut from the cured liner: flexural modulus of 250,000 psi, flexural strength of 4,500 psi, and wall thickness no more than 5 percent under design. NASSCO wrote these rules for public sewer contracts, not house lines. On a house line, ask before the job whether a cured sample will be kept for testing.
Testing has limits. NASSCO notes that water leak tests make little sense on small lines cured with air pressure. Germany’s IKT institute found one in eight liner samples from job sites missed at least one target value.
Ask for the before and after footage and keep it. For the full process, see how CIPP pipe lining works.