Laboratory experiments to establish design and operating criteria for an in-field rinse system to clean agricultural pesticide sprayers are in progress. Current work has been directed toward quantifying the operating parameters which affect the cleaning of the fluid reservoir using a rinse nozzle manufactured for agricultural applications. Degree of cleanliness was determined from rinsate samples collected from a fluid reservoir that had once contained a potassium bromide solution. A portable pH Meter equipped with an ion specific bromide electrode was used to measure chemical residues. An initial KBr concentration of 10,000 ppm was used to fill sprayer tanks prior to rinse tests. Laboratory test apparatus were designed, constructed, and modified to test a variety of agricultural sprayer tanks. Three sizes of polyethylene sprayer tanks (190, 380, and 760-L nominal capacities) were subjected to the KBr solution and later rinsed with the tank rinsing nozzle applying clean tap water. Rinse tests consisted of filling a sprayer tank with the KBr solution, draining, rinsing, and measuring rinsate concentrations. Four pressures (138, 207, 276, and 345 kPa), two rinse volumes (5 and 10 percent tank capacity), and three rinse procedures (triple, double, and single rinse) were evaluated. Total rinse volumes were applied in applications equal to the rinse procedure. Preliminary results indicated the triple rinse procedure with a 10 percent tank volume reduced KBr residue concentrations below 10 ppm over the range of tank sizes tested.