Hi I have a swimming pool surround that I need to clean tomorrow it was only cleaned a month ago by his gardener but didn't come out clean. So wants me to clean. I used a weak hypo mix about 6 to 1 to see if it cleaned it. The surface is some sort of rubber so didn't want it too strong. Can I make it stronger and how long should I leave it on for will pw it first. Can I use my turbo nozzle on it.