Low voltage testing has several different terms such as EFVM (Electric Field Vector Mapping), LVIT (Low Voltage Integrity Testing) or just LV Testing. Regardless of what term you choose it is all a form of Electronic Leak Detection & Leak Testing (ELD).
How does the Low Voltage ELD work
The low voltage method utilizes the conductive properties of water to create a signal when there is a voltage drop to help test and locate leaks in the roof membrane. The process starts with a conductive boundary cable being laid down on the roof membrane which goes around the perimeter of the roof or designated field you choose to test. All roof penetrations such as roof drains an any other conductive penetrations not coated in membrane or liquid applied products must be shunted off properly to keep the field clear of any potential voltage loss. Then the roof membrane is sprayed down with a thin layer of water so the entire surface in the test field is wet. After wetting the surface, the generator is connected to the positive terminal on unit. The negative terminal is connected to a suitable reference or ground on the building’s structure. There is now a low voltage field created for testing the waterproof membrane.
When there are leaks in the roof membrane that allow water to penetrate to the building’s structure, a short circuit is created. The detector unit which is the 2nd piece of the low voltage test equipment is connected to two hand-held test probes (poles), a positive and negative, which are held in contact with the roof surface. By measuring the differential in voltage between the test poles, the detector unit is able to direct our technician to the location of the leak or where a breach may be present.
We can perform electronic testing on most flat roof surfaces such as:
- Single Ply Membranes
- Hot Melt systems
- Liquid Applied Systems
- Built-up Felt Systems
- Torch Down
- White EPDM