How to detection leak under insulation

1.water leakage detection by cable

Leak detection cables operate based on physical or electrical changes that occur when the cable comes in contact with a liquid.

2. by Two 1.5 mm copper 

Using two uninsulated  1.5 mmcopper wires for leak detection is a standard method used in industrial pre-insulated piping (such as district heating pipelines) and for commercial water leak detection cables.

The detection principle relies on the following mechanisms

The Detection Principle

• How it works: The two uninsulated \(1.5\text{ mm}\) copper wires are embedded parallel to each other inside the pipe or cable's insulation layer. A continuous, very small electrical current or voltage is applied to the wires. [
• The trigger: Because the copper wires are uninsulated, dry insulation acts as a barrier, causing the system to read a high electrical resistance. [
• The leak: When water or moisture (which conducts electricity) penetrates the insulation layer, it bridges the gap between the two copper wires, creating a short circuit or a drop in resistance. System Implementation

• Hardware required: You need a dedicated Leak Detection Module or controller.
• Location tracking (Reflectometry): Advanced controllers use Time Domain Reflectometry (TDR) or impedance analyzers. They send a pulse down the wire and measure the bounce-back to calculate exactly how many meters down the pipe the water leak is occurring.
• Sensitivity: These systems are highly sensitive and generally allow you to configure different sensitivity thresholds so that normal ambient humidity won't trigger a false alarm
• 3. by sniffer bottle