Disposing of rainwater into a private sanitation system is prohibited and we strongly advise against connecting a gutter to the BIOROCK system. Doing so may lead to non-compliance.
On the one hand, the amount of water cannot be controlled and on the other hand, rainwater is polluted with dust and various types of residues, which, in large amounts, tend to, in comparison with domestic effluents, upset the balance. The bacteria need organic matter and the disposal of rainwater will "rewash" the system during a shutdown period. Excessive water will lead to system inefficiency
Talk to your local product product specialist.