FAQs Drip line precipitation rate formula:231 X GPH___________________(spacing X distance) Metric Formula:60 X l/min__________________(spacing X distance) 231 is going to be the conversion number or constant.The GPH depends on the size of the built in emitter, Hunter manufactures .4, .6 or 1.0 GPH (1.35, 2.35, 3.75 l/hr) emitters in PLD.Spacing is the emitter spacing, Hunter manufactures 12, 18 and 24 inch (30, 45, 60cm) emitter spacing.Distance, is the sideways measurement between the lines of drip installed.You can also find a chart in the catalog on page 117 that has the application rates calculated for different combinations. Still need help? We're here. Tell us what you need support with and we'll find the best solution for you. Contact Support Previous article Flow Rates Next article Maintenance