Hi @godsten, thanks for reaching out. The Iro builds watering schedules based on the zone attributes selected. Without going into the math used to build these equations, the vegetation type and nozzle selection are biggest variables in determining the water needed and how long to run the system. Every lawn is different and our default values might need to be overridden to fine tune the Iro to your lawn's needs. Drip zones in particular can be VERY hard to build watering schedules for as the nozzle output can range from less than 1 GPH to over 30 GPH. If you could email us at email@example.com with details of each zone in questions (plant type, nozzle make/model, nozzle spacing, etc) our support team would be happy to help you research your system's infrastructure and landscape watering requirements to fine tune the Iro's scheduling algorithms.
Hope this helps!