Green pool? Here's how to clear it, step by step

Green water is algae. It shows up when there isn't enough chlorine working in the water, usually after a warm spell, a storm, or a pool that sat closed too long. The good news: it's almost always fixable in a few days.

Step 1: Clean out what you can

Scoop out leaves and debris with a leaf net. Don't vacuum yet if you can't see the bottom; you'll clog the filter. Empty the skimmer and pump baskets.

Step 2: Test and fix the pH

Chlorine works poorly when pH is high. Test the water and bring pH down to around 7.2 before you shock. This one step makes the shock far more effective.

Step 3: Shock it, hard

A green pool needs a much bigger dose of shock than a weekly treatment, and darker green needs more. Add it in the evening with the pump running, and follow the product label for a pool your size.

Step 4: Run the filter around the clock

Keep the pump on 24 hours a day until the water clears. Clean or backwash the filter whenever the pressure climbs. The filter is doing most of the work at this point.

Step 5: Brush and vacuum

Brush the walls, steps and floor every day to knock algae loose. Once the water turns cloudy blue or gray, the algae is dead; vacuum it out, to waste if your filter allows.

Step 6: Rebalance

Test again and bring chlorine, pH and alkalinity back to normal. If the water stays cloudy, a clarifier and more filter time usually finish the job.

Keeping it from coming back

• Keep chlorine in range all season, especially in hot weather
• Run the pump long enough every day
• Brush weekly, even when the pool looks clean
• Open early in spring while the water is still cool
• Clean the filter on schedule