A device used to detect the presence of a leak in the piping of a remote pumping system.

More than half the leaks that occur in underground fuel storage systems originate, not in the tanks, but in the piping. A leaking pipe can be particularly serious if the system is pressurized.

A pressurized pumping system is one where the pump is located at the tank end of the piping rather than at the dispenser end. In a pressurized system, when even one dispenser is in operation, all the lines served by that dispenser’s pump are filled with product under pressure.

If a leak should occur in any one of these lines, the pressure created by the operation of the pump could cause a large amount of fuel to be quickly released into the ground. To guard against this, the federal underground tank regulations require that pressurized systems be equipped with automatic line-leak detectors. An automatic line-leak detector is defined in the rules as any device capable of detecting a leak of 3 gallons per hour when the line pressure is 10 psi, within 1 hour.

Detectors are usually installed at the pump end of the piping, although some models are installed under the dispenser. The most commonly used detectors operate on a pressure principle. As long as piping remains pressurized, the line-leak detector remains inactive. But if pressure is lost in the pipe, the detector goes to work. Inside the detector is a spring-loaded control that requires a predetermined level of pressure to open. When the submerged pump is turned on, if the line is unable to build to the predetermined pressure level as a result of a leak in the pipe, the leak detector will not open.

The flow of product that normally moves from the storage tank to the dispenser is blocked. Only approximately 1-1/2 to 3 gallons of product a minute comes out of the dispenser nozzle. This signals the station operator when something is wrong.

Other line-leak detectors include electronic circuits that enable the detectors themselves to turn off the remote pumping units the moment a significant pressure drop or volume loss is detected.