I have a waterfall feature made out of pre-cast pavers, and over the winter there seems to be a few spots where it seems to be leaching stuff from the joints/pavers. It's milky in color, and I tried scrubbing with just pool water, but it seems fairly hard, and was wondering if something more like muric acid might remove it? If it will, what's the best way to go about using it on the waterfall, should I dilute it, do I have to be careful about not getting it on the liner?