I believe there is some circular logic going on here. Within the custom nozzle configuration, the prompt is requesting a “flow rate” metric. However, there is a support article that discusses how custom nozzles use the flow rate to calculate precipitation rate. The issue here is that nowhere in the software do you specify the # of heads/emitters. Thus, the equation cannot be calculated correctly. It would be possible for one to calculate precipitation rate manually using the formula, but there is nowhere to input this figure. Furthermore, the catch cup test can tell you how many in/hour of water your yard receives, but this is quite different than flow rate. A catch cup test only tells you the efficiency of your system, not the flow rate. No where can I find how to calculate flow rate per nozzle other than my taking the meter total over a 15 minute duration, dividing by the number of heads/emitters, and then multiplying by 4. This would tell you gph for entering the flow rate, but once again, mathematically, the software would not have enough information to calculate precipitation rate.