OP
Engineer54
If asked id build a small panel PLC controlled, water level, flow switches and alarm status... Pumps would work as requested if flow switch failed to monitor water flow the pump in question would be locked out and other pump takes over. Alarm would be raised.
A little bit more money but you won't get a call out in the middle of the night saying its flooded because one pump failed.
If were talking about rainwater harvesting, the tanks will be outside, so i can't see a problem with flooding to be honest.
Seen the system using three or four tanks being used for this very purpose all over Southeast Asia, and none of them needed a PLC controlling 3 pumps. If anything, you stand more chance of the PLC going ---'s up, than a pump... Bit different if this system was for an industrial process, i'd certainly agree with you in that instance... I'd be keeping this rainwater system as simple as possible...