FS series liquid flow switch is designed for managing the flow changes when the liquid flows in the pipe, such as water, ethylene glycol or other non-hazardous liquids. When the liquid flow is higher or lower than the setting value, the single-pole double- throw contacts (SPDT) can get through one circuit and at meantime to break the other circuit. FS series liquid flow switch is commonly used for chain reaction or “no flow” protection.