None Cuastic Tfr is fine on Polycarb roofs but no need to use pur water to rinse off as you wont see any spots unlike a Galss roof. Apparently some Polycarb roofs have a coating on them to reflect UV but a mild solution shouldn't be any problem. I dilute 1-20.
Just been reading another post were poeple only use wfp pure water on Con roofs. This works OK but when there is a lot of green algie then Tfr cuts through like butter.
I'm no expert yet, but worked with a guy who's showed me his way and have done a couple myself now and this system works well.
Wayne