Drainage systems are an integral part of any drained tunnel. Improper planning, execution and maintenance can cause sintering and pipe damage, which could mean costly maintenance measures and tunnel closures for the tunnel operating company. In order to minimize maintenance expenditures, it is necessary to identify potential problems that may need to be incorporated into the planning phase of any future projects. The first portion of this paper is focused on the evaluation of maintenance procedures for secondary drainage systems. The bypass tunnels "Hausmannstätten" (Styria), "Grünburg" (Upper Austria) and the tunnel "Reinertshof" (Bavaria) are those that have been evaluated. The goal is to show the reasons behind the existing sintering problems in the drainage systems and the necessary maintenance steps required. Therefore, the building data, prevailing geology and hydrogeology are analyzed, and any maintenance activities carried out on the drainage systems on site are documented. The maintenance measure at the respective pipe sections is defined as the flushing speed. A graphical comparison of the tunnel structure with its drainage system, the prevailing geology and hydrogeology, as well as the achieved flushing speeds shows that, in the area of shaft structures (UT "Hausmannstätten" and "Grünburg"), the flushing speeds are reduced considerably, resulting in an increase of required maintenance for the drainage system. The evaluation of the tunnel "Reinertshof" shows, that the discharge of the pressurized groundwater, via the drainage system, is the cause of the dominant sintering problem. The second portion investigates the influence of solid hardness stabilizers as a pre-sedimentary maintenance method for future maintenance activities on the secondary drainage system of a tunnel structure. For this purpose, a long-term test at the "Zentrum am Berg" research facility evaluates the formation of sintering during the first months of the operating phase. A measurement and observation program compares sections both with and without solid hardness stabilizers. The implementation of the solid hardness stabilizers takes place at the transition of the drainage gravel to the slotted drainage pipe. The evaluation shows that minimum future maintenance efforts can be assumed. The influence of implemented hardness stabilizers could not be fully confirmed due to generally low sintering volumes on the test sections.