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A pressure washer’s size or power is measured in pounds per square inch (PSI). The amount of pressure you need will depend on your project and the material you’re washing, but consumer pressure washers range from 500 to 2,400 PSI. Porous materials like brick and stucco should not be blasted with anything stronger than 1,000 PSI, while you can use a PSI of up to 2,400 to clean a vinyl fence.

You can whiten concrete for unsealed and unfinished concrete with a solution or either muriatic acid or bleach and water—but never both. However, if your concrete does have a stain, finish, or polish, keep in mind that these hard chemicals could damage the topcoat. Your best bet otherwise is to power wash outdoor concrete slabs or clean indoor ones with a gentle cleaner such as laundry or dish detergent.

Yes, pressure washers can remove rust stains from concrete. However, when coupled with an acid treatment, they can be even more effective. Just be sure to use a minimum of a 15-degree nozzle to prevent damage to the surface, and users must also be careful not to get in the way of the pressure washer’s jet as they can cut through skin and cause injury. 

You should avoid using a pressure washer on any surface or item that could be damaged by the high-pressure spray, as some materials are too delicate to withstand the force.

Key items and surfaces to avoid include:

• Electrical Components: Never pressure wash electrical systems, as water can cause short-circuits and create a safety hazard. This includes utility meters, breaker boxes, electrical outlets, generators, and HVAC or air conditioner units.

• Delicate and Fragile Materials: Fragile items can crack, shatter, or be stripped by the pressure. Avoid pressure washing windows, glass, light fixtures, shingled roofs (especially asphalt), and stucco.

• Painted, Stained, or Sealed Surfaces: Unless your goal is to strip the finish, do not pressure wash painted surfaces, stained wood (like decks), or anything with a protective seal that could be stripped away. Be especially cautious with older surfaces that may contain lead paint.

• Soft Woods and Certain Decking: Delicate surfaces like softwood, composite decking, and antique or wooden patio furniture can be etched or damaged. If you must wash wood, use a lower-powered pressure washer with a wide-angle nozzle to prevent damage.

• Living Things: Never use a pressure washer on people, pets, or plants. The force can cause serious injury and will destroy landscaping.