My pressure washer is out of service at this time (carb needs cleaning). My house was turning black. It's supposed to be white. I tried the easy to do DIY solution. I bought a bottle of house wash at lowes that went on the garden hose. No prep, no pre-wash or anything like that. Just spray it on, let it sit 5-10 minutes (don't let it dry out) and then turn the hose nozzle to the power stream setting and hose off the house. It took me a little over 30 minutes to do the front of my house. I started by wetting down one end of the house, worked to the other end and then went back and started the hose off process. Not difficult at all. It did a good job. It says it reaches up to the 2nd story, but my experience was that it stopped being effective at abut 1.75 story. Top piece of siding could have used more attention, but I wasn't getting out the ladder for a 2 foot long section. It can stay slightly off white. The stuff I bought was in the pressure wash chemical area, not in the area with the general cleaning supplies.