De Dietrich RCI 300 Instructions Techniques, D'installation Et D'entretien page 24

1.7 Use and maintenance
1.7.1 Operation
The pump is operated by a pressure switch which controls the level
to which the tank is filled. When the condensates have reached the
maximum authorised level, the pump is triggered and evacuates the
neutralised condensates until they reach the minimum level. This
operation is repeated in accordance with the filling cycle.
1.7.2 Maintenance
The neutralisation station must be checked at least 1 time per year.
If necessary, replace the granules. The effectiveness of aggregrate
neutralisation can be checked by verifying the pH of the neutralised
condensates at the appliance outlet (using litmus paper).
If the pH is less than 6.5, the neutralisation station must be cleaned
and the aggregate replaced. The latter is not harmful to the
environment and can be disposed of with household waste without
any risk.
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DU15 04/12/2013 - 8541-4017-02