Generally speaking electronic leak detection is used for locating leaks on underground water lines. Leaks above the slab and under raised foundations (wood floors), are not discernable with conventional leak detecting equipment and are better and more economically dealt with by conventional means.
Sewer and drain line leaks are best located with sewer cameras. To begin with it should be determined that there is a leak under a concrete floor, before initiating electronic leak detection. Signals are a hot spot on the floor, the sound of water running when all plumbing fixtures are not in use and water coming from someplace on the floor (ground floor), or at a low point on a wall (1st story). Hot water coming from a cold tap and a water heater that doesn’t shut off, or re-ignites quickly, are other signs. At that point one should check the water meter. If the needle is moving and no plumbing fixtures, or bibs, are in use, then there is definitely a leak somewhere. If the main shut-off valve is closed and the meter’s needle stops, it indicates that the leak is in the house (building). Otherwise it is occurring between the meter and the dwelling.
Once it is determined that the leak is in the house, the house shut-off valve can be reopened (causing the meter needle to resume movement) and the hot water shut-off valve, located on the cold water inlet to the water heater, can be closed. If the needle again stops moving, it means the leak is on the hot water line.
Once it has been determined where the leak is, the loss of water can be controlled by closing either the hot water heater shut-off valve, which will still leave you with the permanent use of cold water, or by closing the house shut-off valve, if it’s a cold water leak, which will leave you with no water. If there is not substantial water coming into the dwelling, these valves can be re-opened for short term use and then re-closed during times of non-use. This allows the occupants to flush toilets, take showers, wash dishes and laundry, etc., while the diagnoses and repair process is being implemented.
To perform the leak detection, the pipes are disconnected, usually at the water heater, and pressurized with nitrogen. This particular gas is excellent for making a “high-pitched” sound that is easily detected through a set of high-quality head phones using a sophisticated listening device. Once the highest decibel of sound is located, the leak is pin-pointed. Occasionally the sound will transfer through a channel of some kind, usually plastic pipe wrapping and the point of discovery may be a few inches or feet away, but we have experienced better than 95% accuracy with our electronic leak detection equipment