Water ingress in porous concrete structures occurs frequently due to rain, humidity or even water pipe leakages. It can influence the long-term durability properties of structures, since it may contain damaging ions such as chloride which may lead to corrosion of accommodated steel reinforcements. Furthermore, in the case of frost, water expands inside the concrete and causes microcracks. Hence, monitoring of water ingress is highly important for maintaining concrete structures and prolonging their service life. On this basis, self-sensing concrete is a promising candidate for this purpose. Fiber reinforced cementitious composites are fabricated broadly by utilizing e.g. polyethylene (PE) fibers. However, those are intrinsically non-conductive and chemically inert. Imparting electrical conductivity to PE fibers gives an opportunity to use them as smart and durable reinforcements for producing self-sensing concrete. Herein, PE fibers were coated via tannic acid modified carbon nanotubes (CNTs) to fabricate highly electrically conductive reinforcing fibers embedded in different concrete matrices. Self-sensory concrete composites were obtained enabling to monitor water ingress. Electrical resistance measurements of smart high-strength (HS) or normal-strength (NS) concrete specimens were continuously recorded during soaking process in deionized water solution. The results demonstrated appropriate sensory properties with relative resistance changes of around 36.1% and 2.5% against deionized water for NS and HS matrices, respectively. Apart from changes in electrical resistance, different graph shapes were found with respect to the types of matrix under investigation. All in all, it suggests that the developed strategy in this paper can be used according to both “pattern” and “intensity” analyses for timely detection of water seepage inside concrete structures.