The forgotten benefit of a "Sump" is that it provides variable water capacity. As evaporation occurs, the water level in the sump can drop without impacting inhabitants in the tank or fuge until your top off system (automated or manual) can correct the problem. Also, any small leak can be overcome by the reserve capacity in the sump. Finally, if setup correctly, the sump can provide capacity to hold water from the sytem that siphons back to the sump during a power outage.