I live in Portland, Oregon and it rains a lot here. I have a composite roof that is 17 years old and I want to treat it with something to remove moss. I have a power-washer and 20" extension wand and I'm wondering if I can use it to de-moss my roof without having to stand on it. I don't like walking on my roof and it's steep. Was thinking that I could either add some de-moss solution to the power-washer and use the wand to spray it over my roof. Or simply hook the extension wand up to water line and mix in some solution to de-moss the roof, but not sure it will have enough pressure to reach the top without the power washer and the right nozzle. Any other thoughts?

Surprised someone has not designed a drone that can fly over a roof and drop de-mossing pellets all over it.

 

What are you calling a "power washer"? Is it a pressure washer, garden pump sprayer, powered tank sprayer???

I have a 4-8' extension wand for my pump garden sprayer and it has an adjustable tip. When set to stream it can spray about 10-12' past the wand so when you add in the 8' wand length and your arm length it can cover reasonably far. I also have a pressure washer and have a 18' long extension pole/wand. That with a zero degree tip can cover pretty far when the engine is at idle. Surprisingly the range decreases as I increase the pressure as it causes misting instead of a stream. I also have an agricultural tank sprayer that pumps 15-20 gpm and with it's zero degree tip it can shoot a stream about 30+ feet beyond whichever want I'm using.

The problem with a pressure washer is it will highly dilute any solution you try to apply so a sprayer that allows you to dispense the chemical directly would be better.

 

Direct injection requires full strength liquid as it does dilute it.
My pressure washer has an injection port. It works in conjunction with an almost open tip.
No pressure activation. It shoots a stream at least 30'.


I have an adjustable spray nozzle that the end pulls out for soap and when you push it back in it goes to pressure wash. It's my favorite nozzle. I wash my entire house with it and no brush required.
variable spray with soap dispense

 

@Pilot Dane - Sorry, was a bit sloppy with my terminology. I have a 2300 PSI electric pressure washer. It's got a soap tank, but not sure if I can put de-mossing solution in it. The water might dilute it too much.

The garden sprayer idea which directly sprays the concentrated chemical sounds like the best approach. I assumed that there is no sprayer that can spray the 15+ feet at up to a 45 degree angle that I need.