Your mix strength sounds about right. I might would do 60/40 bleach water if there is any more than light staining.
Cling on - start with one quart per fifty gallon mixed batch for a nice low slope roof and as much as two quarts per fifty for a steep roof.
No SC needed, no need to monkey with the mix
Get some 3 mil contractor bags to place at bottom of downspouts (You may have to remove the downspout leaders that go out in the yard).
The challenge that I issue to new roof cleaners is to see how little product you can use to clean the roof. It doesn’t need flooded in most cases. More is not necessarily better and enough to kill the growth and remove its color is the exact right amount.
Stop often and check you bags. Remove them before you think you need to.
After cleaning, flush the gutters (again, into bags) to remove the inch or so of roof bleach that always ends up standing in them.
As my old buddy Don Phelps used to say, “Don’t fall off the roof, and don’t kill any plants”. It really is that simple.
Try a small section with your mix. Give it a few minutes to work. If it hasn’t done the job in 5 minutes, mix is too weak. I haven’t worked with cling-on but if you can’t find the info on Pressure Tek’s site, call or email them. I would bag those gutters and release the bulk of your chemical away from landscaping. Better safe than sorry on that one!
Again thanks a lot for the great info guys. Very informative.
Tim. So these 3mil bags will not bust when I pick them up to remove them? I imagine they can only handle so much water, not to mention getting too heavy to lift. So I guess my question is what is considered full to the point I need to replace them?
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If you can’t get the poly tubing just get some heavy duty garbage bags. What I starting doing is bag the gutters, lightly rinse the roof, change out bags, and then rinse the hell out of it. By the time your done it should be so diluted down it wouldn’t kill anything. Sometime I even stick a garden hose in the gutter to make sure it’s diluted down enough. Another local guy laughed at me and said that was overkill but the way I see it is overkill is better than replacing thousands of dollars worth of landscape. Good luck on the job!