Talked to OCF's tech line regarding their position on power washing roofs. They take the same position that is published in the ARMA Tech Bulletin of May 2007. However, when I asked do they themselves outline that in the warranty,or have a separate paper addressing the matter...they said no.
If a claim is turned in by a home owner for granule loss and it is determined that a power washing system was used, the warranty is voided.