No need to bleach, then nuke for 3 minutes, or anything.just Whinks. Transforms a black pipe, (or even the tough, hard to clean burn spots), back to crystal clear. Caution: use rubber gloves! I never let the solution touch my skin and keep it away from your pretty stainless steel sink! Hold it over a garbage can or toilet. Pour it in, shake or let soak, and watch the black stuff turn to flakes. Pipe cleaning (HANDS DOWN, 100% guarantee): Whinks, rust stain remover.