Got black streaks which have developed on composition shingle roof. Googled it etc and it's a form of algae. Seems to be a number of suggested methods to get rid of it, many suggesting the use of bleach water or bleach water with combination of TSP, etc. So far I've tried half and half bleach/water mix sprayed on with a garden sprayer and let sit a while then rinsing off with garden hose nozzle. Didn't seem to help. Some say use a stronger ratio of the bleach, like 2/3 bleach to 1/3 water, which I tried too; still didn't seem to work. Maybe I need to try with the TSP mixed in, which I haven't tried. Apparently the TSP is supposed to work as a surfactant to help keep the bleach water from running off the shingles so quickly so it has a chance to work better. Any comments/suggestions appreciated in this regard. thanks

 

Shingles are difficult to clean without damaging the shingles
Adding TSP or most any detergent should help. I wouldn't be surprised if you can't get it all off.
Generally it's best to pick a shingle color [next time] that won't show the stains as bad if they are an ongoing problem.

 

Yeah not supposed to use a pressure washer so just need to be able to get a cleaning (bleach typically) solution on it and let it soak and then rinse off and hope it works. Of course don't wanna damage the shingles by any scrubbing with a brush etc. Well if any detergent should work in place of the TSP maybe I'll just use clothes washing detergent I think that could less expensive. What I was reading was half bleach to half water and then add a 1/4 cup TSP to that then spray it on with a garden sprayer. Let it sit a while (hard to determine for how long, I guess it depends on the humidity/temperature, just guess I suppose) then spray it off with a regular garden hose nozzle. I'm not worried about harming plants with the use of the bleach, nor worried about a little suds coming out of the downspouts either. Changing out to different color shingles next time that won't show the stains as bad not gonna happen because there aint gonna be a next time.

 

TSP is cheap. Less than $4 for a box at HD. It doesn't go bad so may find another use for it down the road.

 

okay, I'll do some TSP shopping/pricing. We dont have a HD where I live so will probably cost more for me but maybe wont break the bank. Should probably get some on hand anyway, for other stuff down the road like ya say

 

TSP is probably one of the better heavy duty detergents but generally any heavy duty detergent will work. The detergent both cleans and helps the cleaning solution to cling to the shingles giving it more time to work.