Once all the mold is dissolved then you need to “soft wash” the siding. Starting at the top of the quickly wash the siding making sure to cover all the surface area. Work your way from the top down washing away debris as you go. Try to wash away all wet debris that may be stuck to the siding during this step. With 8 GPM we can use the soap nozzles to rinse, it makes it easier and more efficient than using higher pressure. On smaller pressure washers you may have to use the higher pressure nozzles (700-1200 PSI) to effectively reach areas.
Remove the detergent injector from the soap and turn off the shut off valve on the line if installed, or place the detergent injector line in clean water. With an 8 GPM washer you may want to remove the chem injector entirely during the rinse process or build a “Detergent injector by-pass system” because the chemical injector reducing the flow of a 8 GPM pump, limiting your rinsing ability.
After you have washed the siding, you now need to thoroughly rinse the siding from top down. Hold the stream of water over an area and let the water “cascade” like a waterfall as you slowly move down the siding. Do this in sections and completely rinse the siding. A good rule of thumb is when you think you have rinsed enough, rinse again the same amount as the first rinse. Rinsing is critically important. You must rinse off all the soap from the siding to prevent the soap from drying on the surface and possible causing oxidation (hazing) of the siding. Make sure to apply an extra rinse to windows. Then rinse the any plants as you did in the pre-wetting process. Take extra time to rinse the plants, and rinse anything else the soap detergent could have been blown onto (cars, furniture, etc). With enough rinsing the SH and detergent will be neutralized and rendered harmless and eventually it will biodegrade into salt.