5 Things to Know About Using Ascorbic Acid for Iron Stains in Plaster Pools

Ascorbic acid is the most effective treatment for iron stains on plaster. Sprinkle it directly on a small test spot; if the stain disappears within a minute, you have iron.

Lower chlorine to zero before treating the full pool. Broadcast a few pounds of ascorbic acid according to the label, then circulate for 24 hours.

The stain lifts as iron particles, which you must vacuum up. Do not skip this step or the particles can resettle.

Ascorbic acid consumes chlorine and can lower pH. After treatment, shock the pool heavily and monitor pH levels closely.

Always follow up with a metal sequestrant to prevent stains from returning. Without it, iron stains will reappear within weeks.