A pipe laser mounts inside a manhole or at the start of a trench, projects a grade-controlled beam along the pipe centerline, and uses a target inside each pipe to confirm both vertical grade and horizontal alignment simultaneously. Set the design grade percent on the instrument, align to the starting invert, and control each pipe to the beam before backfilling.
A pipe laser is the standard tool for controlling grade and alignment on gravity sewer, storm drain, and conduit installations. Unlike a rotary laser, a pipe laser controls both grade and horizontal direction in a single setup, and the target fits inside the pipe itself — giving you real-time feedback on every joint before you backfill.
Common models: Topcon TP-L6G, Spectra DG511, Leica Piper 200, Hilti PR 30-HV. All project a grade-controlled, direction-controlled beam along the pipe centerline. Some models include remote grade adjustment from inside the trench.
A circular target that fits inside the pipe and shows the laser beam position relative to center. The bullseye shows grade (vertical) and direction (horizontal) simultaneously. Target diameters match common pipe sizes from 6 inch to 60 inch.
The laser mounts on a tripod, a channel iron bracket spanning the manhole, or a pipe clamp depending on the application. Stability is critical — the laser must not shift during installation.
Used to establish the starting invert elevation and to perform independent verification shots at receiving manholes. Always verify the final invert with an independent instrument before accepting grade.
From the plan set, find the design grade percent for each pipe run and the starting invert elevation (manhole invert). Calculate the theoretical elevation drop from start to finish:
Use the grade percentage calculator to verify your elevation drop before setting up the laser. Confirm the end invert matches the receiving manhole invert on the plans.
Mount the pipe laser on a tripod or channel iron bracket at the starting manhole. The laser body must point directly toward the receiving manhole. Use the horizontal adjustment on the laser mount to align the beam along the pipe centerline — sight down the trench or use offset stakes to confirm direction.
For long runs or curved alignments, reset the laser at intermediate manholes to maintain line and grade control. A single setup from manhole to manhole is ideal — resetting mid-run requires re-establishing height above invert at the new position.
Enter the design grade into the pipe laser controls. On Topcon TP-L6 and Spectra DG511 models, press the grade adjustment buttons and read the display. The instrument tilts the beam to match the entered grade — downhill in the direction of flow.
Verify the grade setting by placing the target at two points at a known distance apart (e.g., 20 feet) and measuring the actual beam elevation change. The measured drop should match (Grade% / 100) times distance within 0.01 ft.
Measure from the starting invert elevation (inside bottom of the pipe or manhole channel) up to the laser beam center. Record this offset. The target must be positioned at the same height above the pipe invert at every point along the run so the pipe bottom tracks correctly with the beam.
Most pipe laser targets are designed so the bullseye center corresponds to the pipe invert when the target sits on the pipe bottom. Confirm this relationship for your specific target and pipe diameter before starting installation.
As each pipe section is lowered into the trench, place the target inside the pipe. Signal to the excavator operator or pipe crew to adjust the pipe elevation and lateral position until the laser beam hits the target bullseye. Do not release the pipe until the target shows centered on both axes.
Check that the spigot end is fully seated in the bell of the previous pipe before confirming grade. A partially inserted joint can appear on-grade but will drop slightly when fully seated, taking that section out of tolerance.
At the receiving manhole, independently verify the actual invert elevation using a rotary laser or level and grade rod. Compare to the design invert. The difference should be within plus or minus 0.02 ft for acceptance.
Log the measured start invert, end invert, run length, and grade percent in Gradelog. This data becomes your as-built record and is required for sewer acceptance inspections. Use Gradelog to log and verify your grade shots digitally — free to start.
Always confirm the laser grade setting by checking two points at a known distance before starting installation. An incorrect grade setting affects every joint in the run.
Inspect the beam path before each pipe placement. Soil, water, or equipment in the beam path blocks the signal to the target. Clear the trench and wipe the laser lens when signal quality degrades.
The target must rest at the same position in each pipe section. If the target floats on water in the pipe or leans against the pipe wall, the beam reading does not represent the actual invert position.
Pipe grade can shift before initial backfill if bedding is not fully compacted. Verify the last several joints before beginning initial backfill whenever you stop for more than 30 minutes.
Field Documentation
Use Gradelog to log and verify your grade shots digitally — free to start. Automatic as-built reports for sewer and storm drain installations.
Quality pipe lasers such as the Topcon TP-L6 and Spectra DG511 are accurate to plus or minus 1/16 inch per 100 feet in grade setting. In field conditions, achievable accuracy is typically plus or minus 0.02 to 0.03 feet per 100 feet of run, which meets standard sewer installation tolerances.
Minimum gravity sewer grade is typically 0.4% for 8-inch pipe, producing self-cleansing velocity of approximately 2 feet per second at full flow. Design grade varies by pipe diameter — larger pipes can run at lower percent grades. Always confirm with the project engineer and local jurisdiction.
On most pipe lasers, enter the grade as a decimal percent (e.g., 1.50 for 1.5%) using the grade adjustment buttons. The laser automatically tilts the beam to the entered grade. Verify by comparing the beam elevation at two points at a known distance apart.
Yes. Pipe lasers project a beam that provides both grade (vertical) and direction (horizontal) control simultaneously. The target shows vertical and horizontal position in one reading, which is the primary advantage over a rotary laser for underground pipe installation.