---
title: Water Main Leak Detection with Fiber Optic DAS | DuyuSense
url: https://www.duyusense.com/en/solutions/water-leak-detection-fiber-optic
---

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# How does fiber optic leak detection work in water networks?

Short answer

Fiber optic leak detection turns a cable laid along or inside a water main into thousands of virtual microphones using Distributed Acoustic Sensing (DAS). The flow noise of water escaping a crack, sudden bursts and nearby excavation are reported with a location within metres. It works best on long, linear trunk mains. DuyuSense develops DAS-based monitoring systems and pilots for water utilities.

Last updated: 2026-09-30 · Prepared by: Dr. Serhat Boynukalın, DuyuSense

## Can DAS detect leaks in water mains?

Yes, DAS can pick up the continuous, broadband flow noise that pressurised water makes as it escapes through a crack, joint or valve seal. The interrogator sends laser pulses into the fiber and measures vibration at every point along the line from changes in the backscattered light.

Unlike traffic or pump vibration, leak noise persists at the same location over time. Signal processing weighs that persistence together with frequency content and positional stability to separate a leak candidate from other sources.

The smallest detectable leak is not a fixed number: it depends on pipe material, diameter, operating pressure, distance between fiber and pipe, and soil conditions. Metallic pipes carry leak noise much further than plastic ones, so on PE and PVC mains keeping the fiber close to the pipe becomes decisive.

- Typically tens of km per interrogator, often cited around 40-50 km
- Spatial resolution typically a few metres
- Continuous 24/7 data instead of periodic surveys

## Is the fiber installed inside the pipe or alongside it?

Both are possible: on new mains the fiber goes in the same trench as the pipe, while on existing mains it can in suitable cases be inserted into the pipe. The choice depends on the age and diameter of the main and whether service can be interrupted.

Trench installation is the lowest-cost route on new transmission projects and pipe renewals. Keeping the cable close to the pipe and firmly bedded improves acoustic coupling. In-pipe fiber hears leak noise more directly through contact with the water, but drinking water compliance, hygiene and access point design need dedicated engineering.

Existing telecom fiber along the road can support an initial assessment. If it runs several metres from the pipe, sensitivity to leak noise drops noticeably, so suitability should first be measured with a short field test.

- New mains: cable in the same trench, close to the pipe
- Existing mains: in-pipe fiber or a nearby fiber route
- Telecom fiber: screening and third-party damage monitoring

## Is DAS suited to trunk mains or distribution networks?

DAS performs best on large-diameter, long and linear transmission and trunk mains. One fiber covers tens of kilometres continuously, so the cost per monitored point is low and the consequence of a burst is highest.

Distribution networks consist of many short, branching pipes of mixed materials plus service connections. Running fiber down every street is rarely economical there, and acoustic loggers, correlators and district metered area (DMA) management are better tools.

A sound design combines both: DAS watches the critical trunk mains continuously, conventional methods cover distribution, and all data feeds one non-revenue water process.

## How are bursts and pressure transients captured?

A major burst appears on the fiber as a strong, sudden acoustic event, and DAS reports it with its location within seconds. Where flow and pressure based SCADA alarms only point to an area, this sends the repair crew straight to the spot.

Pressure transients from valve operations, pump starts and stops, and water hammer create dynamic strain in the pipe wall. Tracking them along the main helps show which sections are stressed by repeated surges and supports assessment of burst risk before failure.

For slow, long-term deformation or strain at specific points, Fiber Bragg Grating (FBG) sensors are the complement, giving high-precision point measurements at bridge crossings, valve chambers and sections exposed to ground movement.

- Located alarm at the moment of a burst
- Water hammer and transient tracking along the main
- FBG strain and temperature at critical points

## Can excavation and third-party damage be prevented?

Yes, DAS can detect machinery, digging and drilling along a main route before damage occurs. In urban areas a significant share of damage to water mains happens during utility and road works.

Excavator bucket strikes, drilling and heavy vehicle vibration have distinct acoustic signatures. Event classification separates them from traffic and routine city noise and raises alarms only for persistent activity close to the route. Leak and excavation monitoring run together on the same fiber.

## How does DAS integrate with DMA and SCADA systems?

DAS alarms are passed to SCADA, GIS and work order systems with location, time, event type and confidence level. The leak candidate is then tied directly to the relevant pipe segment on the map.

In district metered areas, minimum night flow analysis shows that a zone is losing water; DAS narrows down where on the trunk main the loss is. Using both sources together shortens search time for field crews and reduces unnecessary excavation.

DuyuSense works with water utilities on interrogator selection, fiber route assessment, signal processing and integration into existing SCADA infrastructure.

- SCADA and GIS integration over standard protocols
- Matching DMA night flow with DAS location data
- Segment-level risk mapping from alarm history

## Why does non-revenue water matter in Turkey?

Non-revenue water in many Turkish municipal utilities remains above international good-practice levels, and the topic is firmly on the regulatory agenda. A regulation on controlling drinking water losses, in force since 2014, set staged reduction targets for utilities.

Non-revenue water combines physical losses with commercial losses such as metering errors and unauthorised use. Fiber optic monitoring targets physical losses, especially leaks and bursts on long transmission mains. Long-distance supply lines serving large cities and urban routes with frequent utility works are natural fits for DAS.

**Comparison of leak detection methods for water networks**

| Method | Strength | Limitation | Best use |
|---|---|---|---|
| DAS (fiber optic) | Monitors tens of km continuously, locates bursts and excavation | Needs fiber close to the pipe, not economical on branching networks | Large-diameter transmission and trunk mains |
| Acoustic loggers | Easy to deploy on valves and hydrants across distribution | Point-based, shorter reach on plastic pipes, batteries and maintenance | Distribution networks and DMA sweeps |
| Correlators | Pinpoint a leak precisely between two sensors | Need an operator and field crew, not continuous | Final pinpointing in a suspect area |
| Satellite (SAR) analysis | Flags suspect zones over wide areas from moisture anomalies | Coarse location, not real time, needs field verification | Prioritising surveys across large networks |
| SCADA and DMA flow analysis | Shows zone losses and large bursts from existing meters | Does not locate the loss on the pipe | Zone-level loss monitoring and alarms |

## Frequently asked questions

### Can DAS detect leaks in water mains?

Yes. DAS picks up the continuous flow noise of pressurised water escaping along the fiber and reports its location within metres. Performance depends on pipe material, pressure and how close the fiber is to the pipe. Metallic pipes carry sound well, while on PE and PVC mains the fiber should be close to or inside the pipe.

### How small a leak can fiber sensing detect?

There is no single threshold. The detectable leak size varies with operating pressure, pipe diameter and material, soil type and fiber position. A reliable answer comes from a short field test on a representative section of the main, ideally including a controlled leak simulation.

### Can fiber be installed in existing water pipes?

In suitable cases, yes. On existing mains fiber can be inserted into the pipe through dedicated access points or routed close to the pipe. In-pipe solutions need separate assessment of drinking water compliance, hygiene and service continuity. On new mains, laying the cable in the same trench is the most economical option.

### Is fiber sensing better than acoustic loggers for non-revenue water?

They suit different jobs. DAS continuously monitors long, linear trunk mains with one fiber and also catches bursts and excavation. Acoustic loggers offer flexible, lower-cost coverage across branching distribution networks. For many utilities the best result comes from a non-revenue water strategy that uses both.

### Can municipal telecom fiber along roads detect water leaks?

Sometimes, but not reliably. If the fiber runs more than a few metres from the pipe, sensitivity to leak noise drops noticeably. The same fiber is usually adequate for monitoring excavation and machinery along the route, however. Suitability should be confirmed with a short field measurement.

### Can DAS be used on distribution networks too?

Technically yes, but many short, branching pipes usually make it uneconomical. The main value of DAS is on large-diameter trunk mains. In distribution, DMA management, acoustic loggers and correlators are better suited, and DAS data can be merged with them in the same loss management process.

### Can DAS alarms be sent to a SCADA system?

Yes. DAS events can be passed to SCADA, GIS and work order systems with location, time, event type and confidence. Operators then see the leak candidate on the relevant pipe segment on the map, cross-check it with DMA flow data and dispatch field crews directly.

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