Ok to use this pressure washer with Wet ‘n Forget? Ryobi GCV 190. I figured it would be no problem to use Spray &amp; Forget/ wet n forget with this .... but now it’s really unclear. Label says mix at between 5:1 and 9:1. This washer has a soap reservoir but manual says it works at 20:1. Maybe that’s fine? 
Side of my house goes up really high so hoping I can make this work. Is using a pressure washer like this uncommon? Thanks!