Architects, Engineers, Builders, Waterproofing Contractors and above all Owners seek watertight waterproofing systems. Typically, after the membrane has been installed, flood testing of some degree may be carried out or ELD testing [Electronic Leak Detection] in the form of High Voltage spark testing (otherwise known as holiday testing) or either of the two forms of Low Voltage leak testing; EFVM known as Vector Mapping and/or IntegriScan [a low voltage membrane scanning platform].
All of the above-mentioned systems form the ASTM7877 Standard Guide for Electronic Methods for Detecting and Locating Leaks in Waterproof Membranes. IntegriScan is the only testing method that meets the now listed standard in the practice of ELD tesƟng ASTM D 8231 – 19. This recent standard came into effect in 2019.
The testing of waterproof membranes is a quality control method to identify breaches, defects or leaks in the membrane before it is covered over, allowing time to repair these deficiencies during or soon after installation. This is the cheapest cost of time and materials to carry out the needed repairs.
The benefits of ELD Testing against flood testing are numerous. Flood testing:
a) Takes 24, 48 even 72 hours and needs to be repeated after a leak is found and repaired to confirm the area is watertight,
b) Wastes time,
c) Wastes a lot of water,
d) Requires temporary dams to be installed to partition off individual wet areas from non-wet areas in buildings,
e) Doesn’t test the full area as walls are not included.
ELD Testing is quick, and efficient and allows for repairs and retesting immediately reducing downtime on site. ASTM 7877[3] Identifies 4 types of ELD testing:
1- High Voltage testing [known as holiday or spark testing]
2- Low Voltage Electric field vector mapping
3- Low Voltage Horizontal membrane scanning platform
4- Low Voltage Vertical membrane surface scanning
Due to differing technology, methodology and some limitations of capability, these differing types of ELD testing units have the same basic requirements. ELD works by creating an electrical field between the membrane surface and a conductive deck or substrate [ie Concrete] which is earthed to the building. When a breach is found the electrical field releases current to complete an electrical circuit; these ELD systems either spark or emit an audible alarm to let the operator know of the breach.
All ELD testing equipment is capable of testing nonconductive waterproof membranes. However, not all ELD testing equipment can find breaches on vertical substrates, multiple horizontal breaches in a single test or test semi-conductive coatings – i.e. membranes such as Black EDPM, Black Butynol or polyurethanes tinted with Carbon black. Only the Low voltage scanning platform or roller can achieve this and therefore meet the current practice standard for leak detection ASTM D8231-19.
1. High Voltage Membrane testing [sometimes referred to as spark testing or holiday testing]. With this form of testing as outlined in the ASTM D7877 guide, a special electrode brush is passed over the surface of the non-conductive membrane. It requires a direct air gap under the brush to the conductive substrate to spark. Testing must be carried out in perfectly dry conditions and should not be conducted in inclement conditions or when dew is present on the surface. Critical with this method of testing is the membrane type and membrane thickness as a correct calibration is key to obtaining accurate results. Liquid membrane coatings generally vary in thickness and with an incorrect calibration, a breach can be missed or the membrane can be damaged by the spark when passed over a thin coating section. Seams on sheet membranes are also difficult for this method to accurately test as the thickness at the seam is doubled; high voltage current cannot travel laterally through a seam defect.
2. Low Voltage Field Vector Mapping involves a perimeter wire being installed around the area to be tested. Within the testing area, grounded objects such as drains and other penetrations must be isolated. This area is subsequently charged up to around 40 volts. Water is then applied to the area within the perimeter wire ensuring full coverage of the surface is achieved. If there are only puddles on the surface, then the circuit would be incomplete resulting in missed breaches. Two probes are used to identify breaches and will always be directed to the strongest breach. Detected breaches will need to be repaired before further testing can be carried out. In areas where there are multiple breaches, further testing needs to be undertaken each time until no more breaches are identified. This can be a time-consuming process if the original waterproof membrane applicator is not on site to rectify any detected faults immediately. Given Vector Mapping requires a constant flow of water over a substrate, vector mapping is not able to test vertical substrates – even with an additive in the water to create a film on a given vertical surface, the accuracy is still not reliable. Vector mapping has been used in the past to test for membrane breaches through overburden in planters and roof gardens, however again the results are unreliable as additional layers of drainage cell, geotextile, protection board and the like interrupt the signal thus providing an unreliable result.
3. The final type of ELD tesƟng listed in the ASTM D7877 guide is the low voltage horizontal membrane scanning plaƞorm. This unit consists of two metal sweeps to make electrical contact on the substrate which has been previously sprayed with water before the plaƞorm passes over it. The outer sweep isolates the testing area under the plate while the inner sweep gives off a visible and audible alert when passing over a breach. Due to technical advancement in the reliability of this method, plus its ability to test both non-conductive and semi-conductive membranes enables this method is the only system to meet the criteria for ASTM D 8231-19 – the practice of testing waterproofing membranes.
4. The low voltage Vertical Surface Scanning roller listed under the guide for testing vertical substrates works by moistening the roller sleeve as the operator rolls the testing tool up the substrate forcing the water before it into any breaches. This low-voltage roller vertical system is also the basis for ASTM D8231 -19.
Electronic Leak Detection [ELD testing] is fast becoming the preferred testing method for builders, waterproof manufacturers and waterproofing contractors who understand time is money on a building site. However, as waterproofing is not a trade-in in Australia, the understanding, implementation and suitability of the waterproof membrane system installed need to be confirmed it is watertight and installed correctly. Water in some parts of Australia is a precious and expensive resource. Wasting water along with time delays involved with flood testing in areas that are large and deep (as walls can leak as much as floors, joints and penetrations under hydrostatic pressure) is no longer viable nor acceptable.
As with all trades on site, those who hold positions of responsibility in delivering the project want to ensure the technician performing the testing is properly trained in the use of the equipment.
The ASTM [American Standards Testing Method] we have mentioned above are internationally recognized standards and are also recognized in the Australian standards as we do not currently have our own standard for ELD testing.
References:
ASTM D77877-14 Standard Guide for Electronic Methods for Detecting and Locating Leaks in Waterproof Membranes, ASTM International, West Conshohocken, PA, 2016
ASTM D8231-19 Standard Practice for the Use of a Low Voltage Electronic Scanning System for Detecting and Locating Breaches in Roofing and Waterproofing Membranes, ASTM International, West Conshohocken, PA, 2019
ASTM D5957-98-2013 Standard guide for flood testing horizontal installations, ASTM International, West Conshohocken, PA, 2019