Five Star says Starsan is good at PH 3.5 or lower (going towards acidic). It's when it goes above 3.5 towards alkaline that it's no good. I use a radiator filling funnel (wider spout) with coffee filters to filter grainy stuff,pet dander,etc out of my Starsan now & then. It even becomes a hair less cloudy. The radiator filler funnel & coffee filter combo flows a lot better than a regular funnel & coffee filter does as well. Makes the job of filtering go faster.