Trade walkthroughs
How to inspect site utilities
Site utilities — storm, sanitary, water, gas, and electrical duct bank — all end up in a trench that gets closed the same day they're laid. Everything that matters is checked in that open trench: the bedding under the pipe, the line and slope, the joints, and the required testing. Miss it and the only way to prove the line was built right is to dig it back up, so the inspection has to keep pace with the crew and hold the trench open until it's verified.
For the superintendent and QC manager verifying underground utilities against the civil drawings, the utility standards, and the testing lab's results before backfill.
Step by step
Verify trench, bedding, and safety before pipe goes in
Confirm the trench reaches line and grade, that the protective system for the depth and soil is in place before anyone enters, and that the bedding is the specified material and thickness. Trench safety is life-safety scope — verify the protective system before entry; a pipe laid on rock or unbedded subgrade deflects and cracks.
Confirm material, class, and product against the spec
Check that pipe, conduit, fittings, and structures are the specified material, class, and size, undamaged, and match the submittal for each system. A downgraded pipe class or the wrong fitting in a pressure line is a failure you won't see once it's buried.
Check line, grade, and slope
Verify invert elevations, slope, and alignment against the drawings, especially on gravity storm and sanitary where a flat or reverse slope won't drain. Confirm structures — manholes, catch basins, cleanouts — are set to grade and location.
Inspect joints, connections, and restraints
Confirm joints are made per the manufacturer — gaskets seated, solvent or fusion welds done right, thrust blocking or restrained joints at bends and tees on pressure lines. Verify service connections and tie-ins to existing utilities match the drawings and the utility's requirements.
Verify required testing before backfill
Confirm the required tests are run and pass while the line is exposed — pressure and leakage on water and force mains, air or exfiltration on gravity sewer, mandrel deflection where specified, and any bacteriological clearance on potable water. The test in the open trench is the proof; there's no retesting after backfill without digging.
Confirm separation, cover, and marking
Verify the required separation between water and sewer and between other utilities, that cover depth meets the spec and frost requirements, and that tracer wire, warning tape, and marking are installed. Separation and cover are code and safety issues, not just layout.
Check backfill, compaction, and surface restoration
Confirm backfill material, lift thickness, and compaction meet the spec, especially under pavements and structures, and that the testing lab takes density tests where required. Confirm surface restoration matches what was there.
Document each run before it's covered
Photograph the bedding, pipe, joints, and structures with a measure or grade reference before backfill, keep the test reports and any survey as-builts with the record, and log any failing test, wrong slope, or damaged pipe as a nonconformance to correct before the trench closes.
What gets missed
- Backfilling before line, grade, and the required pressure or exfiltration testing are verified.
- Pipe laid directly on rock or unbedded subgrade instead of the specified bedding.
- Flat or reverse slope on a gravity line that never drains and pools.
- Missing thrust blocking or restraint at bends and tees on pressure lines.
- Inadequate separation or cover between water and sewer — a code and health issue found too late.
Questions people ask
- Why does utility testing have to happen before backfill?
- Because the joints and the pipe are what you're testing, and once the trench is closed they're inaccessible. A pressure or exfiltration test in the open trench proves the line holds and pinpoints a bad joint while you can still reach it — after backfill, a failed retest means excavating.
- Who inspects tie-ins to public utilities?
- The serving utility or municipality inspects and accepts connections to public mains and often witnesses the testing, in addition to your QC walk. Coordinate their inspection and the required disinfection or clearance before you rely on the connection, and keep their sign-off in the file.
Standards behind it
Terms worth knowing
Checklists that make this a one-tap job
Free, field-ready checklists, each with the photo every item needs before it can be submitted.
Related guides
- How to inspect sitework and earthworkInspect sitework and earthwork in sequence — erosion control, excavation, subgrade, fill and compaction, utilities, and grading — before each layer is buried.
- How to inspect plumbing rough-inInspect plumbing rough-in before it disappears into the wall or slab: DWV slope, pressure test, water lines, supports and protection, with the proof each needs.
- How to inspect a retaining wallInspect a retaining wall from the foundation up — bearing, reinforcement, drainage, backfill, and the wall system itself — because the drainage and steel are buried behind it.
Reading the steps is one thing. Proving you walked them is the job.
RTI holds the submit button until every mandatory item is answered and the photos are attached, then chains the record so it can be proven untouched later.