A toilet bolt cap liquid sensor including an outer shell defining an interior cavity sized to receive a portion of a toilet bolt and house a liquid sensor; the liquid sensor including an exposed surface to the interior cavity. The liquid sensor can be used in a leak detector system for a toilet comprising: a flat base sheet bound by an outer perimeter an interior aperture; a wick material barrier coupled to the base between the aperture and the outer perimeter in a continuous or substantially continuous strip around the aperture; a wick material projection extending from the wick material barrier; and a toilet bolt cap including an outer shell defining an interior cavity for receiving an end of a toilet bolt, the toilet bolt cap housing the liquid sensor the liquid sensor including an exposed surface to the interior cavity for contact in fluid communication with the wick material projection.