For A number of years, many investigators in California have recognized the need for a portable, lightweight, low cost, effective spray unit that could be used in a variety of field tests–involving chemical treatment of livestock and poultry, barns and similar farm structures, accumulations of animal manures, as well as for field and row crops. A sprayer with such qualifications was needed to eliminate extensive time frequently required to calibrate, adjust, and repair local spray equipment when used in test work. Also needed as a sprayer with which multiple chemical or dilution applications could be made to test units without stopping to clean and refill tanks (as is necessary with conventional farm sprayers).