Conduit Installation
Conduit Verification
TLDR
Conduit verification proves a duct is continuous, round, and clear before a fiber crew mobilizes. A mandrel sized near the inside diameter is pulled the full run, and rodding or camera inspection locates anything that stops it. You receive a documented pass, the measured footage, and a repair record for whatever was found.
What Verification Is Protecting You From
The risk verification removes is a fiber crew standing down. A blow that stalls partway along a run, or a pull that will not go, converts a scheduled production day into locating, exposing, repairing, and reproofing, while the reel sits cut in and the splice schedule slides behind it.
The defects are ordinary and invisible from the surface: an oval section from an overpulled installation, a coupling that separated during pullback, a flat spot where a steel plate sat over a shallow trench, silt and water in a run left open, an intruding root, or a duct punched by somebody else's bore.
Verification is inexpensive and it happens early. It takes place after the duct is in and before anyone commits cable, crew, or a splice schedule to it. That order is where the entire value sits, because every one of those commitments is more expensive to unwind than to delay.
Mandrel Proofing: Sizing and Method
A mandrel is a rigid slug, sized close to the duct inside diameter and long enough that it cannot cock sideways and slip past a deformation. It is pulled the full length of the run on the pull tape, in the direction the cable will travel, and a pass means the duct will accept cable of the size it was designed for.
Sizing is the decision that makes the test meaningful. A mandrel much smaller than the duct passes obstructions that will later stop a cable, which is worse than not testing at all, because it produces a documented pass that is not true. We size to the project specification for that duct and record the mandrel used alongside the result.
Direction matters too. Proofing in the direction of the planned installation catches a step at a coupling that a pull from the other end would ride over without noticing. Where a run will be blown from an intermediate point or in both directions, it is proofed to match how it will actually be used.
Rodding, Camera, and Finding the Problem
When a mandrel stops, the footage on the pull tape tells you approximately where. Rodding confirms the stopping point and often identifies the kind of obstruction by feel. A duct camera gives you a picture instead of a guess: a collapse, a separated coupling, a foreign bore driven through the duct, or standing debris and water.
Locating that point on the surface uses the tracer wire, or a sonde pushed to the obstruction, which is one more reason the tracer system matters. The excavation becomes a single small dig at a known point rather than a search along a route with a backhoe and an optimistic estimate.
Repair means a rated coupling and a replacement section, not tape and not a sleeve improvised on site. After the repair the full run is proofed again end to end, because a partial retest only proves the part you were already worried about and says nothing about what the repair excavation may have done elsewhere.
Verifying Conduit You Did Not Install
Inherited duct is the most common place a project quietly loses time. Legacy conduit records overstate size, understate occupancy, and describe routes that were changed in the field and never redrawn. Building a schedule on that record is a risk you can retire in a day of verification instead of discovering during construction.
Verification of existing conduit starts with locating and proving the route, then proofing what is actually there: real inside diameter, whether the path is continuous between the access points you intend to use, and whether the duct is already partly occupied or already damaged somewhere in between.
The output is a decision, not just a report. Some runs are usable as found, some need innerduct to be usable, some need a repair at a now known point, and some should be abandoned in favor of a new bore. Knowing which is which before you commit a schedule is the reason to do it.
The Verification Record You Receive
Every verified run comes back with its identifier, the measured footage between access points, the mandrel size, the result, the date, and the crew. Where a run failed, the record adds where it stopped, what was found, what was done about it, and the reproof result after repair.
Measured footage is worth more than it looks. It gives your splicing group a real distance for slack planning, gives your maintenance group a reference for interpreting OTDR distances later, and quietly corrects the design footage that everyone would otherwise keep using for the next decade.
The verification record travels with the as-built into your closeout package, so each duct is documented as a proven path rather than a line drawn on a route map and assumed to be open.
Where Does Verification Fit in the Build Schedule?
Verification belongs after restoration and before the cable crew is booked. Backfill, compaction, and paving all put load on a shallow duct, so a run proofed before the ground is closed can still fail later. Proofing after the surface work is done tests the duct in the condition the cable will find it.
On long routes, waiting for the whole build to finish wastes time. We proof by section as each one is restored, so the fiber crew can start on verified sections while placement continues elsewhere. That keeps the two crews moving in the same direction without the cable crew catching up to unproven duct.
Lead time is the other reason to verify early. If a run fails, the repair needs a locate ticket, an excavation, and sometimes a permit notice before any digging starts. Finding the problem a week before cable is scheduled leaves room for all of that. Finding it the morning of the blow leaves none.
What Proofing Results Tell an OSP Engineer
A pass is more than a checkbox. The measured footage replaces design footage in slack calculations, splice planning, and cable orders, which keeps the next cable from being cut short or ordered long. It also gives the maintenance group a true distance between access points for reading OTDR traces during a future fault.
A pattern of failures tells you about the installation, not just the run. Repeated oval sections point to pull tension problems. Separated couplings point to joining practice. Flat spots near the surface point to backfill or equipment loads. Those patterns matter when the same crew or method is still placing duct on the next phase.
For inherited conduit, results feed a go or no go decision for each run. A route that looked usable on paper may turn out to need innerduct, a repair, or a new bore. Knowing that before the schedule is set is cheaper than learning it with a reel on site.
Key takeaways
- Conduit verification moves the discovery of a crushed or separated duct from the day the fiber crew arrives to a day when it only costs a repair.
- A mandrel sized well below the duct inside diameter produces a documented pass that is not true, which is worse than no test at all.
- After any repair, the full run should be proofed again end to end, not only the section that was fixed.
- Inherited conduit records often overstate size and understate occupancy, so existing duct should be verified before a schedule depends on it.
Key terms
- Mandrel
- A rigid cylinder, sized close to a duct's inside diameter and long enough that it cannot tilt past a deformation. It is pulled through a finished run on the pull tape. If it passes, cable of the design size will pass.
- Duct rodder
- A long, stiff, flexible rod on a reel that is pushed into a duct by hand or machine. Rodding confirms where an obstruction sits, gives a sense of what it is by feel, and can carry a sonde or a pull line through the duct.
- Sonde
- A small battery powered transmitter pushed into a duct on a rodder. A locator on the surface finds its signal, which marks the exact point above an obstruction so the repair can be one small excavation instead of a search.
- Pull tape
- A flat, low stretch tape, often printed with sequential footage and sometimes called mule tape, left inside a duct after installation. It carries the mandrel during proofing and later pulls in cable or a winch line, and its footage marks show distance along the run.
| Method | What it proves | What it misses | When to use it |
|---|---|---|---|
| Mandrel proof | The duct is continuous and round enough for the design cable | Pinholes and small leaks | Every run, before cable is scheduled |
| Air or pressure test | The duct is sealed and holds pressure | Oval sections and partial crushes | When the specification calls for it, often ahead of blowing |
| Rodding | Where an obstruction sits along the run | A clear picture of the cause | After a mandrel stops short |
| Duct camera | What the obstruction actually is | Conditions beyond its reach | To decide on a repair before excavating |
| Sonde and locator | The surface point above the problem | Duct condition itself | To fix a single dig location |
What this means for your project
Verification is the cheapest schedule insurance on an underground build. A failed blow stops a crew that is already paid for the day, with a reel cut in and splicers waiting downstream. A failed proof costs a locate, a small excavation, and a reproof, all of which can happen before anyone else is committed. The difference is timing, and timing is the whole value of the service.
On inherited conduit, verification turns an unknown into a decision. Before a route is priced and scheduled on the strength of an old record, a short verification effort shows which runs are usable, which need innerduct or a repair, and which should be replaced. That keeps a change order from appearing in the middle of the cable phase.
The record is part of the deliverable. Per run results, mandrel size, measured footage, and repair history go into the closeout package, giving your engineering and maintenance groups a verified starting point for the next cable, the next fault, and the next audit.
Related reading
- Fiber pullingCable placement that depends on a proofed duct with pull tape in place.
- Locate and repairFinding and fixing damaged duct on existing routes, including runs that fail verification.
- Tracer wire installationThe locating system that turns a mandrel stop into a single surface dig point.
- Closeout and documentation standardsWhat a complete closeout package should contain, including duct test records.
- Daily production reportingHow proofing results and repairs are reported while the work is still underway.
- Resources for OSP engineersHow we support engineers who need verified footage and duct records for design.
What's Included
- Mandrel proofing on every run, sized to the project specification and pulled the full length in the planned installation direction
- Pull tape or mule tape verification, with tape reinstalled where it is missing or broken
- Measured footage between access points recorded and compared against the design footage
- Rodding and duct camera inspection on any run that does not pass
- Obstruction location using tracer wire or a sonde so the excavation is one known point
- Repair with rated couplings and replacement duct, followed by a full length reproof
- Verification of existing and inherited conduit including real inside diameter, occupancy, and route
- A documented result per run, pass or fail, with mandrel size, footage, findings, and repair detail
Our Process
- 01
Scope and Sequence
We agree which runs get verified, in which direction, with what mandrel, and on what schedule relative to your fiber crew. On long builds we proof by section as sections complete rather than holding everything until the route is finished.
- 02
Proof Pull
The mandrel is pulled the full length on the pull tape in the installation direction, footage is measured, and the result is recorded per run. Passing runs are resealed and plugged immediately so they do not take on silt while waiting for cable.
- 03
Diagnose and Locate
On a failure, the stopping footage is noted, then rodding or a duct camera identifies the obstruction and a tracer locate or sonde fixes it to a surface point. You get the location and the cause before anyone opens ground.
- 04
Repair and Reproof
The section is exposed at the located point, repaired with rated couplings and replacement duct, and backfilled. The full run is then proofed again end to end, and both the original failure and the reproof pass go in the record.
- 05
Document and Release
Each run is released to the cable installation crew with its footage, mandrel result, and any repair history attached, so the fiber schedule is built on verified paths rather than assumptions carried over from the design.
Capability Overview
| Proofing method | Rigid mandrel pulled the full length on the pull tape in the planned installation direction |
|---|---|
| Mandrel sizing | Sized to the project specification relative to duct inside diameter, recorded with the result |
| Inspection | Duct rodding and camera inspection on any run that does not pass |
| Obstruction location | Tracer wire locate or sonde pushed to the stopping point to fix a single dig location |
| Repair | Rated couplings and replacement duct section, followed by a full length reproof |
| Existing conduit | Route locate, real inside diameter, occupancy check, and continuity between planned access points |
| Output | Per run pass or fail record with mandrel size, measured footage, findings, and repair detail |
Frequently Asked Questions
- When should conduit be proofed?
- After the duct is installed and before any cable is committed to it. Proofing after backfill and restoration is important, because backfill itself is a common source of flat spots. Proofing before the fiber crew is scheduled is what protects the production day. On long builds we proof by section as sections finish rather than waiting for the entire route to complete.
- What does it mean if the mandrel stops halfway down a run?
- Something is reducing the inside diameter at that point: an oval section from an overpull, a separated or offset coupling, a crushed spot under a load, or a foreign bore driven through the duct. The footage on the pull tape gives an approximate location, and rodding, a camera, or a sonde narrows it to a single dig point for repair and reproofing.
- Can you verify conduit that another contractor installed?
- Yes, and it is one of the most useful things you can buy before committing a schedule. Inherited duct records are often wrong about size, occupancy, and route. We locate and prove the route, confirm real inside diameter, check continuity between the access points you intend to use, and report which runs are usable as found, usable with innerduct, repairable, or better replaced.
- Is an air test the same thing as mandrel proofing?
- No. A pressure or air test looks for leaks and confirms a sealed system. A mandrel proves geometry: that a rigid object of a known diameter can travel the full length of the run. A duct can hold air and still be too deformed to accept the cable it was designed for, so the mandrel is what tells you the path is usable. We run air tests where your specification calls for one.
- Should spare ducts be proofed too, or only the ones getting cable now?
- Proof the spares too. A spare duct is placed so someone can use it later without digging, and that only works if it is open. Proofing it now, while the crew and access are already there, costs very little. Finding a crushed spare years from now means a new excavation in a corridor that may be paved, landscaped, or crowded with other utilities by then.
- How long does conduit proofing take?
- It depends on run length, access, and what the mandrel finds. A clean run with pull tape in place and open structures at both ends proofs quickly. Missing pull tape, flooded handholes, or a failure that needs rodding, a camera, and a locate all add time. We schedule proofing by section ahead of the cable crew, so that time comes out of float rather than out of a production day.
- Who pays when a conduit run fails the mandrel test?
- Your contract decides that, and the verification record makes the answer clear. When we proof our own work and a run fails, we repair and reproof it. On inherited conduit, the record shows where the run stopped, what was found, and what the fix requires, so the owner can decide on repair, innerduct, or a new bore with facts in hand instead of an argument about who caused the damage.
Related Services
- HDPE Conduit PlacementHDPE conduit placement by directional bore, trench, or plow in Central Florida: wall rating, fused joints, controlled pull tension, and sealed, proofed runs.
- Tracer Wire InstallationTracer wire installation in Central Florida: direct bury wire placed with the duct, waterproof splices, test stations, continuity testing, and locate walks.
- Fiber BlowingFiber blowing and jetting into HDPE duct and microduct across Florida. Duct proofing, low tension placement, and continuous runs with fewer splice points.
- Fiber PullingFiber optic cable pulling through Florida conduit and duct. Monitored pulling tension, correct swivel and grip rigging, lubrication, and bend radius control.
- As-Built DocumentationAccurate as-built records captured in the field during construction, not reconstructed afterward. Coordinates, depths, photos and reconciled footage.
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