Liquid leak detectors sense when a liquid is leaking from a pipe, tank, or other receptacle area.  With most liquid leak detectors or fluid monitoring systems, an alarm or indicator alerts the user based upon the accumulation of liquid, the pressure difference, or change in flow.   

Electrical conductivity or resistance is generated when the liquid contacting both probes completes a conductive circuit in most cases the tank or vessel is included in this circuit.    Liquid leak detectors use a low-voltage power source applied across separate electrodes.  An electrochemical sensor or a selective chemical sensor may measure the presence or concentration of liquid chemicals. The output is presented as an amperometric, conductometric or potentiometric electrical signal.  The signal is often relayed to a process controller.  This technique can be used with fluid process equipment including pumps, valves, seals, storage tanks and confined spaces in a variety of industries and applications.  

Mass balance and mechanical float based liquid leak detectors identify the rise and/or fall of level or flow of the process liquid.  The flow meter identifies a flow differential.  The level sensor uses sealed reed switches in a stem with a permanent magnet installed in the float.  As the float rises or falls, a switch is activated.  This signal may be relayed for automatic shut off. 

In a pressurized system, mechanical line liquid leak detectors report a loss of pressure in a liquid or fluid distribution line.  A piston operated valve or pressure vacuum switch indicates leakage.  A positive pressure or vacuum sensor can detect pressure change in interstitial space of double-walled tanks.  This type of system can be used in pipelines between storage tanks in the petroleum and oil industries. 

Based on the absorption and collection of electromagnetic radiation, optical leak detectors use optic sensors and the principle of optical refraction to detect presence or absence of fluid.  Typically, LEDs are utilized as the source of light.

Ultrasonic liquid leak detectors identify the ultrasonic noise created by a liquid or gas moving through a small orifice, or they recognize the attenuation and dielectric properties of the liquid or air present (piezoelectric SAW devices). Alterations of acoustic wave propagation can transmit information relating to the intensity and consistency of the leak in water distribution systems.  The process liquid type and temperature may be considered when choosing this type liquid leak detector.

Liquid leak detection systems can use a number of indications including LEDs, audible alarms, and remote interfaces for control and analysis. Some systems include result summaries to monitor the leak in a line or tank in aerospace, water, waste, petroleum and oil, food and beverage, hydraulic, medical, and pharmaceutical applications.