Advanced Acoustic Leak Detection in a 100-Year-Old Raw Water Main in Bristol

Executive Summary

In July 2024, Aganova, in collaboration with SUEZ UK, carried out a high-precision internal inspection of a 6.7 km raw water main operated by Bristol Water in North Somerset, South West England. The asset, a 100-year-old cast iron pipeline, is a critical part of the utility’s water supply network and had become increasingly difficult to assess using conventional methods due to its rural location and lack of surface leakage indicators.

To address this challenge, Nautilus in-line acoustic inspection technology was deployed. This next-generation system is designed to detect non-visible leaks, air accumulations, and structural anomalies without interrupting service, while also delivering high-resolution hydraulic data for network management.

The inspection was completed under live operating conditions and revealed three anomalies, including a major leak (F1) with an estimated loss of 0.8 million liters per day (MLD). Within days, the leak was exposed and repaired, enabling the recovery of approximately 1 MLD and preventing further long-term losses.

Beyond the immediate repair, the project delivered a comprehensive dataset, including precise GIS-based incident mapping and pressure and elevation profiles generated by the upgraded Nautilus system. These insights provide Bristol Water with a robust foundation for targeted maintenance, risk reduction, and long-term asset planning, while reinforcing its commitment to efficient and sustainable water resource management.

Client

Partner

Sections

6.7-kilometer raw water main

Location

North Somerset, South West England

Date

July 2024

Diameter

33” and 24”

Speed (m/s)

Min

Max

0.4

Pressure (bar)

Min

Max

Distance (m)

6,695

Introduction

Bristol Water is responsible for supplying drinking water to over 1.2 million people across the South West of England. Ensuring the integrity of its network is vital to maintaining a safe, reliable, and sustainable service.

Among its critical assets is a cast iron raw water main more than a century old, transporting large volumes of untreated water through rural North Somerset. With its age, strategic role, and difficult access points, this pipeline required a detailed assessment using innovative tools capable of delivering actionable insights without service disruption.

For this purpose, Bristol Water turned to Aganova’s Nautilus technology, an advanced in-line acoustic inspection system capable of detecting leaks and anomalies that remain invisible to traditional methods

Challenge

The primary challenge was the age and condition of the pipeline, which increased the likelihood of hidden deterioration. Its remote rural setting limited accessibility and monitoring options, while the absence of surface leakage indicators made it impossible to detect problems externally.

Bristol Water therefore needed a non-invasive and highly accurate diagnostic solution that could operate in live conditions, locate hidden anomalies with precision, and at the same time generate additional hydraulic data to support long-term asset management.

Solution and Implementation

The inspection process included the following stages:

Insertion: The Nautilus sphere was introduced through a DN150 gate valve using a disinfected pressure chamber, enabling safe insertion in just 37 minutes without service disruption.
Synchronizer Installation: Eight synchronizers were placed along the 6.7 km pipeline, with two checkpoints to monitor progress. Each device was installed in about 10 minutes, ensuring centimeter-level incident localization.
Navigation: The sphere entered the pipeline at 14:09, was detected at checkpoints at 14:13 and 15:50, and completed the journey in 2 hours under flow conditions of 312 L/s.
Extraction: The sphere was retrieved at 16:50 through a second DN150 gate valve. Disassembly and cleaning were completed in 25 minutes, ensuring efficient, non-invasive recovery.

The pipeline inspected had the following characteristics:

Pipeline

Characteristics

Location

North Somerset, South West England, UK

Pipeline material

Cast Iron

Diameter

33” and 24”

Water speed

1 m/s (25 Ml/d) – 0.4 m/s (10 Ml/d)

Pressure

1 – 6 bar

Insertion point

DN150 gate valve

Extraction point

DN150 gate valve

Aerial view of the pipeline inspected

Pipeline elevation profile

Pipeline pressure profile

Installation of Synchronizers along the pipeline to ensure accurate incident localization.

Extraction of the Nautilus sphere using a non-invasive retrieval system mounted on DN150 valve.

Results

Leaks

Incident Severity

1 incident

Air

Incident Severity

0 incidents

Anomalies

Incident Severity

Total incidents

The post-inspection analysis identified three anomalies:

1 major leak (F1) with an estimated flow loss of 0.8 MLD
2 air-related anomalies (A1)

Nautilus also provided a detailed pressure and elevation profile of the inspected pipeline section.

Using the exact coordinates delivered by Aganova, Bristol Water exposed and repaired the F1 leak, recovering approximately 1 MLD of water. The absence of visible surface leakage confirmed that this was a long-standing hidden failure that would not have been detected without advanced in-line inspection.

Conclusions

This inspection demonstrated the effectiveness of in-line acoustic diagnostics in identifying high-impact, non-visible leaks. The collaboration between Aganova, SUEZ UK, and Bristol Water enabled the targeted repair of a major leak and immediate water recovery, while ensuring the continuity of service throughout the process.

Beyond the operational impact, the project provided strategic value: a complete hydraulic profile of the pipeline, accurate GIS mapping of anomalies, and data to guide preventive maintenance and investment planning. By adopting Nautilus technology, Bristol Water has strengthened its approach to reducing non-revenue water, extending asset life, and building a more resilient and sustainable network for the future.