Wettable powders are abrasive by nature and will cause wear to the Viton® collar, piston pump and cylinder of the model 425, 435 sprayer. The Solo models 474, 475, 476 and 485 sprayers with a diaphragm pump are generally resistant to abrasive materials and are recommended for this purpose. Note: If you use a wettable powder in your 425, 435 sprayer, be sure it is thoroughly mixed in the formula solution. Immediately after use, be sure to remove the piston, clean and lubricate the Viton® collar with Solo Superior Grease or petroleum jelly. Thorough flushing of sprayer will extend the useful life of its working parts. If you use wettable powders in the piston pump sprayer be sure to inspect regularly for seepage around the piston and repair accordingly.