An adapter includes an interface module that receives signals from a first sensor that indicate a first fill status of a holding tank. A control module of the adapter generates a control signal based on the first fill status. The toilet is at least partially controlled by a toilet control module that restricts a flush capability of the toilet based on the control signal. An isolation module of the adapter isolates the interface module and the control module from at least one of voltage and current fluctuations that are external to the adapter.