Electronic Leak Detection | Build Meets World (EP. 06)

Key Concepts

• Electronic Leak Detection (ELD)
• Low Voltage Scanning Platform
• Low Voltage Vector Mapping
• Low Voltage Vertical Roller
• High Voltage (Spark Testing/Holiday Testing)
• Conductive Substrate
• Conductive Medium (e.g., TruGon conductive primer)
• ASTM D7877 (Standard Guide for ELD)
• ASTM D8231 (Standard Practice for Low Voltage Scanning Platform and Vertical Roller)
• Overburden (drain mat, insulation, soil, gravel, topping slabs)
• Inverted Waterproofing Assembly
• Conventional Roof

Introduction to Electronic Leak Detection (ELD)

• Definition: ELD is a generic term for four different methods used to pinpoint breaches, holes, and seam voids in roofing and waterproofing membranes by applying an electrical current to the surface.
• Basic Principle: An electrical current is applied to the exposed membrane. The current flows through any breaches to a conductive substrate underneath, completing the circuit back to the equipment.
• Typical Waterproofing Assembly: Membrane applied directly to structural concrete, which acts as the conductive substrate.

Requirements for ELD

• Conductive Substrate: Must be directly under the membrane (structural concrete, metal, or a conductive medium like arc conductive primer).
• Ground Connection: A metallic or conductive element connected to the substrate and penetrating the membrane (e.g., metal drains, exposed rebar, lightning rods, HVAC units, or earth touching the concrete structure).
• Exposed Membrane: ELD cannot be reliably performed through any overburden (drain mat, insulation, soil, gravel, topping slabs) as these block the electrical path.
• Electrical Path: An electrical path from the top of the membrane to the conductive substrate is essential. Low voltage ELD uses water to carry the current, while high voltage can spark through air.

Industry Standards for ELD

• ASTM D7877 (2014): A guide listing the four ELD methods, describing testing apparatus, procedures, and limitations. It provides a general framework for ELD.
• ASTM D8231 (2019): A practice specific to the low voltage scanning platform and vertical roller methods (DTEC Systems). It expands on D7877 and reflects technical advancements in ELD.
  • Advancements: Includes the ability to test semi-conductive membranes like black EPDM or Tremco's 250 GC roller grade, which was not possible when D7877 was initially published.

High Voltage (Spark Testing/Holiday Testing)

• Origin: Developed in Europe in the 1960s for testing coatings on pipes.
• Application: Works on horizontal and vertical surfaces, transitions, and details.
• Limitations:
  • Cannot be used on conductive membranes (e.g., black EPDM, Tremco's 250 GCR).
  • Requires completely dry conditions; inclement weather, frost, dew, or pooled water can cause false positives.
  • Voltage must be adjusted for membrane thickness; incorrect voltage can burn the membrane or miss breaches.
  • Not ideal for seam void detection as the spark travels vertically through air, not horizontally.
• Process: A technician uses a broom or brush apparatus to apply up to 40,000 volts to the membrane surface. A spark indicates a breach.

Low Voltage Vector Mapping

• Origin: Developed in Europe in the 1970s for testing pond liners.
• Application: Works on horizontal, non-conductive surfaces.
• Limitations:
  • Cannot be used on conductive membranes (e.g., black EPDM, some moisture-cured fluid coatings).
  • Requires isolating the testing area with a wire, which means transitions and areas around grounded objects cannot be tested.
  • Requires a large amount of water; gaps in water coverage can lead to missed breaches.
  • Generally not used on vertical surfaces due to feasibility issues.
• Process: A wire is set up to isolate the testing area. The membrane is flooded with water, and the equipment detects current flow through breaches.
• Overburden Claims: While some claim it can test through soil or gravel, this is only possible in very limited situations where the probes can physically contact the membrane and the area is flooded. Insulating materials like drain mat, root barrier, or insulation block the signal. The ASTM standard states that insulating layers block the leak locating signal, which can only be bridged with water saturation.

Low Voltage Scanning Platform and Vertical Roller (DTEC Systems)

• Development: Created specifically for roofing and waterproofing to simplify ELD and address limitations of other methods.
• Advantages:
  • Faster and easier to use.
  • Can test both horizontal and vertical surfaces (with the vertical roller).
  • Better leak locating sensor due to detecting breaches through water.
• Low Voltage Scanning Platform:
  • Designed for horizontal surfaces only.
  • Can test both non-conductive and semi-conductive membranes, including Tremco's 250 GC roller grade.
  • Has a built-in isolation area.
  • Uses a secondary sensor bolt, allowing the technician's body to become an extension of the equipment for testing difficult-to-reach areas.
  • FM approved for FM conventional roofs.
• Low Voltage Vertical Roller:
  • Works on horizontal and vertical surfaces, transitions, and details.
  • Currently only works on non-conductive membranes (but vertical conductive membrane testing is coming next year).
  • The technician saturates the roller in water and drags it across the surface; the equipment alarms at the location of a breach.
• Limitations:
  • The platform only works on horizontal surfaces and requires a wet surface.
  • The roller must be saturated with water.
  • The roller currently does not work on black EPDM or semi-conductive coatings (but an update is planned).

Comparison of ELD Methods

| Feature | High Voltage | Vector Mapping | Scanning Platform | Vertical Roller | | ------------------------ | ------------ | -------------- | ----------------- | --------------- | | Inverted Assembly | Yes | Yes | Yes | Yes | | Conventional Roof | Yes | Yes | Yes | Yes | | Conductive Medium Needed | Yes | Yes | Yes | Yes | | Dry Conditions | Yes | No | No | No | | Pinpoint Breach | Yes | Yes | Yes | Yes | | Transitions/Verticals | Yes | No | No (Platform) | Yes | | Seam Void Detection | No | Yes | Yes | Yes | | Conductive Membranes | No | No | Yes | No (Currently) |

Specification Tips

• Scope Language: Use the term "electronic leak detection" to encompass all four methods from ASTM D7877.
• ASTM Standards: Include ASTM standards in new construction specs to hold testing agencies accountable.
• Timing: Specify that testing should be done at the last possible moment before covering with overburden or starting a warranty.
• Conductive Membranes: If a conductive membrane (e.g., 250 GC) is specified, use language like, "Perform electronic leak detection using the low voltage scanning platform in accordance with ASTM D8231."
• Conductive Substrate: Ensure a conductive substrate (usually structural concrete) is present under the membrane. Chemically cured concrete and lightweight insulating concrete are not sufficiently conductive.
• Non-Conductive Substrates: Cover board, insulation, wood, and lightweight insulating concrete require a conductive medium to enable ELD testing.

Conductive Medium: TruGon Conductive Primer

• Description: A water-based primer with carbon black that makes it conductive.
• Approvals: Tested and approved by Tremco for hot fluid and cold fluid coatings, UL listed, and FM approved.
• Application: Painted onto the substrate, allowed to dry, then the membrane is applied.
• Benefits: Enables ELD testing on the membrane for its entire life.

Fully Monitored Systems

• Application: Available for inverted assemblies and conventional roofs.
• Process (Inverted Assembly):
  1. ELD testing is performed on the membrane, and breaches are repaired and retested to establish a baseline.
  2. Sensors are installed on the membrane surface, isolating the membrane into zones.
  3. The area is immediately covered with drain mat to protect the membrane and sensors.
  4. Over time, water penetrates the assembly and reaches the sensors.
  5. Each zone charges the water with a low voltage current.
  6. If a hole occurs, the water flows through the membrane, touches the concrete, and completes an electrical circuit.

Conclusion

ELD is a valuable tool for detecting leaks in roofing and waterproofing membranes. Understanding the different methods, their limitations, and the importance of proper specification and installation is crucial for ensuring effective and reliable leak detection. The use of conductive mediums like TruGon conductive primer can expand the applicability of ELD to a wider range of roofing and waterproofing systems.