 A pressure washer alone is enough to clean most surfaces. Stubborn stays or heavy build-ups of dirt, mold, or mildew sometimes need the added help of a cleaning detergent for complete removal. Fortunately, most pressure washers have a cleaning solution injection system for such applications. Some even have onboard detergent storage tanks for added convenience. There are several brands and types of cleaning solutions on the market today. Whichever you choose, make sure it's designed for use in a pressure washer. It should say so, right on the label. If it does not say it, don't use it. Never use bleach or bleached-based products as they can damage your pressure washers pump and kill vegetation. Cleaning solutions come in both ready to use and concentrated formulas. Ready to use solutions can be used right out of their container. Concentrated solutions need to be diluted with water. When using concentrated solutions, mix in a new container according to the manufacturer's directions. Once you have your cleaning solution ready to go, check to make sure that the cleaning solution injection tube is securely attached to the pump. Then insert the other end into the cleaning solution. If your pressure washer has an onboard storage tank, make sure the shut-off valve is turned to the on position. A pressure washer will only siphon cleaning solutions when in low pressure mode. So a low pressure soap nozzle must be used. For added effectiveness, a rotating scrub brush attachment can be used to apply cleaning solutions. On vertical surfaces, always apply cleaning solutions from the bottom up to avoid streaks. Most solutions need to dwell five to ten minutes before rinsing. Re-wet as necessary. Don't let it dry. When it's time to rinse the surface, switch to the high pressure spray pattern that's appropriate for your cleaning project. If you were using an onboard storage tank, turn the shut-off valve to the off position. Make sure any remaining solution is flushed from the system. Rinse the surface from the top down. This again reduces the chance of streaking. Even though most pressure washer cleaning solutions are biodegradable, always flush the surrounding area with plenty of clean water.