One of the benefits of a drop in liner is that if it is damaged it can be easily repaired. However, that does require being able to locate the damaged area to know just where to repair the liner. The first step is to make a visual inspection and see if the hole can be located that way. If not visually noticeable we recommend the use of a high frequency spark tester.
A high frequency spark tester is a hand held device that can produce a voltage from 6,000 to 20,000 V. There are several different electrodes that can be attached depending upon the testing being conducted. We prefer the use of the pointed electrodes but wire brush electrodes can also be used. The voltage setting of the unit will depend upon the thickness of the liner and the conductivity of the tank behind it. There are two main types of spark testers.
When the tank is suitable for entry the use of a high frequency spark tester can be employed. The electrode of the tester is passed over the lining in a sweeping, continuous stroke. A pinhole leak will be seen as a white or blue arc jumping from the spark tester wand through the lining to the metal. If a leak is detected this area is marked for repair. Once the liner has been fully inspected and detected holes can be repaired using either the hot air welder method or the flexible PVC adhesive method.