Mechanical seals are the most diffuse solution for rotating shaft sealing because of their high safety performances and low maintenance costs. The only requirement to meet high service level is a care in the choice of a sealing system suitable for fluids treated and operating conditions. Mechanical seal manufacturers usually have very large catalogues with a wide mix of products for each use and also offers to their clients customized solutions and maintenance service. This could result in high inventory cost for manufacturers which want to guarantee high maintenance service performances. This study shows a reliability driven methodology to reduce the mix and maintain high performances.