07 Understanding Sonde Tracing & Dye Testing

Some drainage information simply can't be confirmed using a CCTV Camera Condition Inspection alone.

Where additional investigation is required, our Comprehensive Architect CCTV Camera Condition Inspection includes specialist techniques such as electronic sonde tracing and dye testing to provide a more complete understanding of the drainage system.

Sonde Tracing

Sonde tracing uses a small electronic transmitter attached to the CCTV camera or drain rod. As it travels through the drainage system, a handheld receiver detects its position from ground level, allowing the approximate route and depth of the underground pipework to be identified.

This information can help:

• Identify the route of concealed drainage. 

• Assist with drainage drawings. 

• Support Build Over Agreement applications. 

• Reduce uncertainty during project planning. 

Understanding the Limitations

Sonde tracing provides indicative results rather than survey-grade coordinates. Accuracy can be influenced by factors such as ground conditions, pipe depth, buried services, reinforced concrete and electrical interference.

Where precise positioning is required, additional surveying methods may be recommended.
→ Learn more in our Glossary: Sonde Tracing

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Dye Testing

Dye testing uses a non-toxic coloured dye introduced into a drainage system to confirm where water discharges.

It's particularly useful where CCTV inspection alone cannot confidently determine:

• Which appliance connects to which drain. 

• Whether drainage systems are interconnected. 

• Surface water and foul water connections. 

• Shared drainage arrangements. 

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In some situations, access to neighbouring properties may be required to fully confirm drainage connections, particularly where shared drainage systems are involved.

Dye testing provides valuable additional evidence when drainage layouts are unclear or multiple drainage systems are present.

→ Learn more in our Glossary: Dye Testing