Fire Service Main Leak Detection

A fire sprinkler system's underground supply main is a pressurized line like any other, and it fails like any other: at a joint, at a thrust block that moved, at a rock pressing on the pipe. The sign is a system that loses pressure between inspections, a jockey pump that runs more than it should, or a wet spot along the main's route from the street to the riser room. Because the main is often large, deep and buried under a parking lot, finding the leak by digging is a very expensive guess.

We locate it acoustically. The method is the same as on a water main: trace the route, listen along it with the ground microphone, and bracket the run with correlator sensors at the post indicator valve, the hydrant, the riser and any other accessible point. The leak is marked with a depth estimate and the location is handed to the owner and the fire protection contractor who maintains the system.

The repair of a fire service main is coordinated work. The fire protection contractor handles the system side, the impairment notification and the retest; we handle the excavation to expose the main at the marked spot and the backfill afterward, and we can make the pipe repair under their direction where that's the right arrangement. The point is that the parking lot is opened once, at the break, rather than along the whole run.

When a property needs this

• A fire sprinkler system that loses pressure between inspections
• A jockey pump running more often than it used to
• A wet area or settling along the fire main's route
• A failed hydrostatic test with no visible cause
• Due diligence on an older system before a building sale

How the job runs

1. Coordinate. With the owner and the fire protection contractor on access, system isolation and impairment procedures before any work.
2. Trace. The underground main's route from the street connection to the riser traced and marked.
3. Correlate and pinpoint. Sensors at the PIV, hydrant, riser and other access points bracket the run; the ground microphone confirms the break.
4. Mark and report. Location, depth estimate and photos delivered to the owner and the fire contractor.
5. Expose. Excavation at the mark through lawn, gravel or asphalt, with the site secured, so the repair can be made at one spot.
6. Backfill and restore. After the repair and retest, bedding, compacted backfill and surface restoration.

What the owner or board receives

• Traced route of the underground fire main
• Marked leak location with depth estimate
• Written report with photos for owner and fire contractor
• Excavation and backfill at the repair point

What shapes the scope

• Depth and size of the main
• Surface over the route, usually asphalt
• Access points for sensors
• Coordination and impairment requirements