Can the output of an external filter decrease?
The motors in the pump heads of the JBL CristalProfi external filters are so-called synchronous motors, this means they rotate with a fixed speed that is dependent on the mains frequency, e.g. 3,000 rpm at 50 hertz.
Accordingly, an external filter can’t lose output. If the flow rate decreases, this is either due to soiled filter media or the formation of so-called biofilms, particularly in the hoses.
Please clean the hoses regularly with a hose brush to remove the biofilms. Flushing with warm water is not enough. At the beginning the cleaning interval may be increased.