Since the Environmental Protection Agency (EPA) started banning the use of pressure treated wood due to chromated copper arsenate (CCA), most people have decided to seal their wood decks as the EPA suggests to prevent the arsenic from leaching into the soil. Most homeowners use local companies to pressure wash their decks and siding to save valuable time and the expense of rental equipment and some prefer to do the job themselves on a hot summer day. If you decide to hire a contractor to perform.