Sometimes it is obvious that you have a plumbing leak. You see water spurting from a pipe or pooling on the ground. Other times, however, the signs that you have a leak may be more subtle. Your water bills may have increased, or perhaps your water pressure has dropped. You suspect there's a leak, but you're not positive, and you certainly don't know where it is. Situations like this call for a plumber. There are a few different methods they can use to tell whether you have a leak and determine exactly where it is.
1. Infrared Thermography
If your plumber suspects a leak may be located in a pipe that runs under a floor, behind a wall, or above a ceiling, they may use a tool called an infrared thermography camera to locate the leak. This camera basically shows you the temperatures of a surface. The warmer areas light up yellow, orange, and red, and the cooler areas stay green and blue. If a part of the wall shows up as blue where the rest of the wall appears warmer, that can indicate a leak in a cold water pipe. Similarly, a red section on the wall can indicate a leak in the hot water pipe.
Another method plumbers can use is to hold a special type of microphone and speaker up to the wall. This option works well when the leak is suspected to be in a large, main pipe that runs under a thicker slab of concrete. If the plumber hears a trickle or the noise of running water, they know they have located the leak. They might even let you have a listen; hearing the water run behind a thick slab can sound pretty cool.
Sometimes leaks occur further down pipes that are mostly located below ground. In such a case, sending a camera down the pipe is usually the best option. Usually, a video camera is used, so your plumber will have a couple minutes' worth of footage demonstrating where the leak is located and how the pipe around the leak looks. They can use this footage when they repair the pipe, which will involve sending sealing equipment down into the pipe. If the leak is bad enough, they may need to dig up and replace the pipe.
As you can see, plumbing leak detection can be an intricate process. However, plumbers spend a good portion of their day doing this, so you can count on their expertise.