Systems and methods for detecting underground voids, comprising steps of: digging a tunnel to be the detection path; placing fluid dispensing means along the bottom part of the tunnel wherein said dispensing means further equipped with fluid pressure sensing means; partially sealing the tunnel as to allow a reasonable portion of the fluids dispensed from said fluid dispensing means to travel downwards, deeper into the ground; providing remote device in data or mechanical communication with said sensing means; on initial activation, allowing pressured fluid to be dispensed from said dispensing means until predefined constant pressure threshold in the system is met; maintaining predefined constant pressure range in the system by constantly or periodically dispensing fluid via said dispensing means; constantly or periodically monitoring said pressure sensing mean; and upon detection of abnormal low pressure in the system activating alert means.