Now that we know what size tip to use we need four pressure tips, a nozzle to apply soap high, one to apply soap low, a nozzle to rinse high with more pressure, and a nozzle to rinse low with more pressure. Depending on your location it may be hard to find a varieties of pressure washing nozzles in local stores. In that case you will have to order the nozzles on the internet. Northern Tool usually has a good selection of nozzles and you could check there for the appropriate nozzles for your machine. Based on our example 3000 PSI 8 GPM machine, we will need a 2520 "Green" nozzle for rinsing low, a 0020 "Red nozzle" for rinsing high, a 2560 "Black soap" nozzle for soaping low, and a 0060 "Black soap" nozzle for soaping high. The numbers "2520" are usually imprinted on the end of the nozzle. The first to numbers is the spray angle 25 degrees "25", the next two numbers are the rated orifice size "20". Unfortunately you may find it hard to find a "0040" 0 degree black soap nozzle in a store. In that case I recommend going to www.pressuretek.com to find a 0 degree soap nozzle. The 0 degree soap nozzle is essential for applying soap to the higher areas of a home. We use a JROD 4 way nozzle holder that holds 4 1/4 meg nozzles at once which gives easy access and makes it harder to lose the nozzles.
Start from the bottom and apply the detergent to the siding as far up as you can reach. Then switch to 0 degree 60 nozzle to reach the higher areas of the siding and the fascia. Make sure all the siding is covered with the detergent. You do not have to "saturate" the surface, just "wet" the surface with the detergent. The secret of efficient washing is multiple quick applications, not long saturating applications that just waste detergent on the ground. Then switch back to the "Green" 25 degree 60 orifice nozzle and spray the siding away from plants to empty the detergent from the lines.
Then immediately rinse any windows from a distance to prevent the solution from drying on the windows. Never spray windows up close with pressure, this can break the vapor barriers of the windows causing them to fog. Always rinse the windows at a distance with low pressure.
Once approximately 5 minutes have passed, apply a second application of "House Wash" mix to the siding. You can move faster now that you are re coating the surface. Pros will coat a larger area (two sides of a small to medium house), then walk back to the start for the 2nd application. By the time they have finished the 1st application, the starting area is ready for the 2nd application and no time has been wasted.
You should see the mold begin to turn brown and run down the siding, if there any areas still containing mold after a few minutes reapply the detergent solution to those areas. If there are any very stubborn mold spots you can use pressure up close to remove them, or use a brush or rag if you can reach the area. Also note our solution will only effectively remove mold, if there are clay stains, grease stains, or heavy dirt stains on the siding you may have to switch to a stronger soap solution or brush the area to remove the stains.
After two applications of "House Wash" check the gutters and siding for any stubborn mold spots that remain. If you still see mold, switch the detergent injector to the "Strong Wash" bucket and spot clean the mold areas only. You can use the 0020 tip to clean the outsides of metal gutters to remove stubborn mold, be careful not to hit the shingles or siding with that tip. You can also use a brush to speed up removal of stubborn areas on gutters and siding while not waiting for the SH to work.
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.