The water used in the Dart was actually a mix of water and methanol alcohol, typically 60% - 40% water to meth. It was used to either restore power - as with the Dart 529, or boost power - as with the Dart 532.
The F-27 had two forty US gallon tanks, one in each aft nacelle, and the FH-227 had one tank, in the left nacelle. Depending on the ASC, the G1 had either two wing tanks, one outboard of each fuel tank, or one tank located in each wing fillet.