After 15 years for systems which are not permanently under water, and after 25 years for systems permanently under water, specific tests must be conducted to check the durability of the installation. These tests involve, among other things, conducting endoscopies, in order to check the internal condition of the pipe network and to determine whether corrosion or the presence of bulky objects will become a problem for water distribution through the pipes. Other observations may also be made during an endoscopy, such as the growth of MIC (Microbiologically Influenced Corrosion). In addition, different sections of the pipes (top, side and bottom) in the network will be measured for thickness, as well as several areas of the installation, depending on its width, in order to check the way in which the pipes are ageing and any potential thinning of the pipe walls. These measurements will be used to check parameters that are not visible without these specific tests and will emphasise potential parts of the installation which need to be replaced or re-verified sooner than expected.