Has anyone had success in adding herbicide to their EZ-Flow system? I have a 2.5 gallon unit serving two softball fields with 5 zones per field and a schedule of watering one field per day for 30 minutes. Our softball season is over in Northern Minnesota. Just for the heck of it i poured a quart of concentrated Ortho weed killer in the tank but I'm thinking this was insufficient. Any suggestions or testimonials out there?