Old thread. Output seems way too high. Suppose at the speed you are traveling and with the swath you are using...you cover 4000 sqft per minute. So if you intended to apply .25 gals per thousand sqft... Your output from the nozzle must be at one gal per minute. Try it a few times with carefully measured water on a big square yard. Add exactly one gallon and spray until one gallon is used up--measure the exact sqft you covered. Adjust pressure as needed and repeat until consistently accurate. Be sure to use a constant speed and a constant swath width. Use Excel and make a fill chart and cover it with plastic and glue it to your tank. Make a few spares as water always gets under the plastic protection.