Accoustics
All leaks which are larger than a weep or drip will give off an acoustic signature which can be detected using powerful microphones. Water hissing out of a faulty fitting below flooring in front of a radiator can be picked up by putting the magnetic microphone on the valve or body of the radiator. We can also attach a bell microphone to the detector which sits on reasonably flat flooring or external surfaces and picks up leak vibrations. The third application is to fit two receivers at either end of a length of pipe and correlate the leak location using the data gathered, this relies on knowing the length and depth of the pipe run along with the pipe size - it can also be affected by branches so is not ideal on complex networks.
Tracer Gas
Tracer gas is a fantastic option where the leak is big enough to allow the cold gas to escape and rise up - this can then be detected using a sample analyser device which gives a loud alert sound and accurate parts per million reading. Detections can be made through most flooring and surfaces with varying degrees of complication, a pipe below loose tongue and groove flooring will be easier than a pipe buried in concrete below a vinyl kitchen floor, given time the gas will still escape to the edges of the flooring and give some indication that the leak is in the vicinity and may well be further pinpointed once the vinyl has been removed.
The gas is 95% nitrogen 5% hydrogen and is harmless as long as there is good ventillation and air flow when released in large quantities
Thermal Imaging
Infra Red technology used for thermal imaging is very useful in determining the location of hot supply and heating pipes under the right circumstances. Pipes low down within a void space or covered with insulation will not show up as well as pipes laid in concrete or close to the surface such as underfloor heating. Even if the conditions are not ideal, the technology can be used to determine the general layout of a property and combined with the acoustics or tracer gas can be a very effective process. I recommend that the heating is switched off overnight so that the background materials are cold giving a nice sharp image when the heating is turned back on, with pipes laid in a solid surface we are looking for an area or areas where the heat image blooms out - this may indicate a damp area which is apreading the heat.
This technology can also be used to find cold and damp spots under the correct circumstances.