Quick Answer
How do you use a pipe laser for CIPP lining?
For CIPP (Cured-In-Place Pipe) lining, a pipe laser is used to verify the existing pipe grade and alignment before lining begins, and to confirm the liner is being inverted on the correct gradient. Set the pipe laser in the upstream manhole pointing downstream, set the grade to match the existing pipe slope (confirmed by invert survey), and use the target on the CIPP inversion equipment to monitor alignment during liner installation. Document grade and alignment data before and after lining.
How to Use a Pipe Laser for CIPP (Cured-In-Place Pipe) Lining
Shop related product: Topcon TP-L6GV Pipe Laser Package at Express Tools →
Applies to: Topcon TP-L6G, Spectra LP51G, Leica Piper 200, AGL LP52G pipe lasers; CIPP sewer rehabilitation projects
CIPP sewer rehabilitation projects use a flexible liner that is inverted through the existing pipe and cured in place to form a structural pipe within a pipe. The pipe laser plays two roles: pre-lining survey verification (confirming the existing pipe has acceptable grade and alignment for liner installation) and installation monitoring (guiding the inversion team to maintain the correct grade during liner inversion). Getting the grade wrong during CIPP installation can create belly sections that trap solids and defeat the purpose of the rehabilitation.
Step 1: Survey the Existing Pipe Before Lining
Before any CIPP crew mobilizes, the existing pipe invert elevations must be surveyed at both manholes and at intermediate access points if available. Use a digital level or total station to measure invert elevations at each manhole. Calculate the actual pipe slope between manholes.
Compare the surveyed slope to the design pipe slope on the plans. Acceptable deviation varies by project specification — typically the surveyed invert should match the design within 0.1% slope. If the actual pipe slope differs significantly from design (indicating pipe settlement, root intrusion displacement, or offset joints), this may affect CIPP installation or require engineering review before proceeding.
Step 2: Set Up the Pipe Laser in the Upstream Manhole
Lower the pipe laser into the upstream manhole and position it pointing downstream toward the inversion access manhole. The laser must be centered in the pipe — use the centering lugs or frame brackets appropriate for the pipe diameter. Level the laser base using the built-in adjusting screws.
Set the grade on the pipe laser to match the calculated existing pipe slope (typically expressed as a percent or as a rise/run ratio). On self-leveling pipe lasers (Topcon TP-L6G, Spectra LP51G), set the target grade using the controller. The beam will be projected on the set grade regardless of the laser housing position. On pendulum self-leveling models, the beam auto-levels and you set grade by adjusting the housing tilt.
Step 3: Verify Laser Alignment Before Lining
Walk the downstream manhole and confirm the laser beam hits the center of the downstream manhole opening. Place the laser target in the downstream manhole and verify the beam hits within 25mm of the pipe center at that distance. If the beam is significantly off-center, the pipe has a horizontal alignment issue that should be documented before lining.
Record the laser grade setting, pipe slope, and any alignment notes in the pre-lining survey record. Take photographs of the laser setup and the target position as documentation for the project record.
Step 4: Monitor Liner Inversion
During CIPP liner inversion, the leading edge of the liner moves through the existing pipe pushed by hydrostatic head (water inversion) or air pressure (air inversion). Place a laser target on the inversion tube or liner head assembly if the system allows. As the liner progresses, the target position relative to the laser beam confirms whether the liner is tracking on grade.
A liner that drops below the laser beam line during inversion indicates the liner is belly-ing — the liner is not filling the pipe cross-section tightly and a low spot may form when the liner cures. Stop the inversion and notify the CIPP contractor's field supervisor if the liner head drops more than 50mm below the laser grade line mid-run.
Step 5: Post-Lining Invert Survey
After the liner is cured and the end caps are removed, survey the invert elevations of the completed liner at each manhole. Compare post-lining inverts to pre-lining inverts. The liner thickness reduces the inside diameter and slightly raises the invert — typically by 6-12mm depending on liner thickness. Verify the post-lining slope falls within the specified tolerance.
Document all pre- and post-lining measurements in the project record. CIPP contracts typically require as-built survey documentation at each manhole to confirm the liner was installed on the specified grade.
Frequently Asked Questions
What pipe laser grade do I set for CIPP lining?
Set the laser grade to match the actual surveyed slope of the existing pipe between the upstream and downstream manholes, not necessarily the design slope. CIPP installs into the existing pipe profile. If the surveyed slope differs significantly from design, document the discrepancy before lining.
Can a pipe laser work in pipes with significant horizontal curves?
Straight pipe lasers project a straight beam — they cannot follow horizontal curves. For curved pipe sections, the laser is useful only for grade monitoring, not alignment. In curved sections, use a CCTV camera to monitor liner alignment during inversion. Some pipe rehabilitation systems use inertial sensors on the liner head instead of laser guidance for curved runs.
What is the maximum distance a pipe laser beam is readable?
Green beam pipe lasers (Topcon TP-L6G, Spectra LP51G) are readable to 300-600 meters in normal pipe conditions. Red beam models are typically readable to 100-200 meters. Dirty pipe, steam, or debris in the air inside the pipe reduces readable distance. Clean the pipe with CCTV inspection and water jetting before CIPP to maximize visibility.
Is a pre-lining invert survey required for CIPP projects?
Most CIPP project specifications require a pre-lining CCTV inspection and invert survey to document the existing pipe condition. The invert survey establishes the as-found grade documentation required for comparing with post-lining as-built data and for confirming the liner was installed on the correct gradient.
Document pre-lining surveys, laser setup records, and post-lining as-built data with Gradelog. Sewer rehabilitation project records organized and shareable. Free to start at gradelog.com.
