To maintain the qualified condition of a pharmaceutical water system, a reliable maintenance plan is necessary. This is an official requirement, though it does also make sense from an operational viewpoint. Maintenance intervals based on the criticality of individual components are usually defined during qualification. But what is the rule here?
One source are the recommendations given by the system suppliers; although operational experiences can also be used for specifying the maintenance intervals. As mentioned before, maintenance intervals are initially determined during the qualification phase. A later extension of these intervals is possible via change control. But what specifications should be used to start with? Are there empirical values for the lifetime of individual components? It can generally be said that membranes in diaphragm valves should be replaced annually. The resin inside the softener should be changed every 3-5 years; this can be seen as a preventive measure against biofilm formation. For reverse osmosis modules as well as ultrafiltration and EDI modules, a preventive replacing every 3-5 years should be scheduled, depending on the frequency of thermal sanitisation. The frequency of on- and off-switching and the quality of the untreated water also play into this. The ozone measuring point of ozonized systems should be replaced every 1-2 years. The UV lamps used for ozone elimination should be changed after 8000 hours of use or after 12 months, at the latest.
These values are merely general reference values; individual cases might call for shorter or longer intervals. A first maintenance plan should be finished by the beginning of the PQ phase.