How to Fix Metal Flashing in Your Pool (Color Change)

Water Changed Color After Shocking

Objective

This guide helps you diagnose "metal flashing"—a phenomenon where pool water suddenly changes color after adding chemicals—and provides the exact steps to sequester the metals and restore crystal-clear water.

The Chemistry of the "Flash"

It is incredibly startling to add a bag of chlorine shock to your pool only to watch the water instantly turn bright green, rusty brown, or dark purple. Don't panic! You did not suddenly spawn a massive algae bloom, and you didn't permanently ruin your water. You are simply witnessing a rapid chemical reaction called "metal flashing."

Chlorine is a powerful oxidizer. If your pool water is secretly harboring high levels of dissolved, invisible metals (often from well water, cheap algaecides, or a corroding heater), introducing a massive dose of chlorine will instantly "oxidize" those metals. Just like iron rusting in the air, the dissolved metals in your pool rust and precipitate into a solid state right before your eyes, tinting the entire body of water. Because this is a chemical issue and not a biological one, adding more chlorine will actually make the problem worse! To fix metal flashing, we must bind the metals together so the filter can safely remove them.

Prerequisites

  • A reliable liquid chemical drop-test kit.

  • A heavy dose of No Mor Stain & Scale™ (metal sequestrant).

  • Clear Treat™ (to act as a filtration aid).

Step-by-Step Instructions: Reversing the Flash

  1. Stop Adding Chlorine: Recognize that the oxidizer caused the reaction. Do not add any more shock, bleach, or chlorine to the water until the issue is resolved. Navigate to your equipment pad and turn your automatic chlorinator or salt cell to the OFF position.

  2. Identify the Metal by Color: The color of the flash indicates which metal is currently suspended in your water.

    • Bright Teal/Green Water: Oxidized Copper.

    • Rusty Brown/Red Water: Oxidized Iron.

    • Dark Purple/Black Water: Oxidized Manganese.

  1. Sequester the Metals: Turn your Pump Switch to the ON position. Add a heavy, curative dose of No Mor Stain & Scale™ directly to the pool water. This formula acts as a molecular magnet, wrapping around the tiny, oxidized metal particles so they cannot stick to your pool walls or tint the water.

  2. Coagulate the Waste: Once the sequestrant has circulated for an hour, add a dose of Clear Treat™ clarifier. Because oxidized metal particles are incredibly fine, the clarifier will clump them together into larger masses that your filter can easily catch.

  3. Run the Filter Continuously: Leave the pump running 24/7. Your filter must do the heavy lifting of physically removing the sequestered metals from the water.

  4. Clean Your Filter: After 48 hours, the water should return to a clear, sparkling blue. However, all that metal is now trapped inside your filter! You must backwash your sand/DE filter or deep-clean your cartridges, otherwise the metals may eventually wash back into the pool.

Troubleshooting Note: When the Metal Sticks

If you successfully clear the water but notice that the green or brown color has plated itself onto your pool plaster or vinyl liner, the metal flashing reaction has caused a physical surface stain. You will need to drop your chlorine levels and use a targeted reducing agent to lift it.

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