The group is providing the only part of the machine which needs regular maintenance. In the absence of maintenance the piston is encrusted and shower plate fills residue to close.
The seal of the piston rod until it hardens to lose grip and water and steam can escape from the connecting rod, the ring also Seeger holding the washer drilled rusts easily. The pins of the lever with prolonged use and consume the ring benzig their firm may emerge from its position. In some cases the pin leverage and the film can rust and become a single body impossible to disassemble
The piston gaskets lose elasticity and adhesion, it becomes difficult to raise and lower the lever and drop water from the filter.
Stating that the machine was revised to say it cleaned and have replaced worn parts.