Abstract: A galvanic cell is formed when ground water within a sump reservoir, tub or other pool, rises to contact electrodes constructed of dissimilar metals, the electrodes mounted in a bridge, with recessing, expansion brackets, to facilitate covering the sump hole and including an alarm device adapted to provide a warning signal should the water level exceed a predetermined level to contact the electrodes. Because an unsealed sump well is the major point of entry of radon gas, an scintillator with associated circuitry monitors the sump well to protect against the undesirable intrusion of radon gas. When the presence of radon is detected, an audible alarm is sounded when the level exceeds 4 picocuries per liter (4 pCi/L.).

Abstract: A galvanic cell is formed when ground water within a sump reservoir, tub or other pool, rises to contact electrodes constructed of dissimilar metals, the electrodes mounted in a bridge, with recessing, expansion brackets, to facilitate covering the sump hole and including an alarm device adapted to provide a warning signal should the water level exceed a predetermined level to contact the electrodes.