Abstract: A liquid-tight lining which is resistant to chemical attack for catch reservoirs, containers or the like of concrete. The lining includes a continuous liquid-tight impervious layer provided above the surface of the concrete. To make possible a simple and safe and repeatable testing of the tightness of the lining, a porous intermediate layer is provided between the concrete and the impervious layer. At least one sensor cable having at least two conductors is placed in the intermediate layer in such a pattern that any location of the intermediate layer is not more than a certain maximum distance away from the cable. The sensor cable is connectible to an electrical monitoring unit.