I was watching Ask This Old House this morning.

They installed a high efficiency combo boiler and WH, a neat little unit
that hung on the wall. Rich pointed out the condensate pump and the
Limestone Neutralizer cartridge stating that the condensate water can be
acidic. He noted that the pump sends the condensate to the sink.

Why do we have to be concerned about acidic condensate going down a sink
drain? Could it be septic tank related? They didn't say anything about a
septic system.