Considerable amounts of water are being lost due to leaks. One of the main reasons for experiencing such large water leaks is the premature failure of rubber sealants in valves. Water leaks commonly originate from the presence of chlorine ions in tap water. Here, we demonstrate that the incorporation of surface-modified and highly crystalline carbon nanotubes allows the rubber sealants to maintain their sealing properties without experiencing any distinctive degradation over a wide range of temperature and environmental conditions over their expected lifetime. It is envisaged that environmentally friendly nanotechnology will save huge amounts of energy for purifying and transporting water around the whole world.