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Green Pool Water? How To Fix It Fast

  • Writer: Heather Pieczonka
    Heather Pieczonka
  • Jul 31
  • 3 min read

There’s nothing inviting about jumping into a green pool. Whether it’s a hint of green or full swamp mode, discolored water means your pool chemistry has fallen out of balance and algae has taken over.


Don’t worry, though. A green pool doesn’t mean you need to drain it or start over. With the right steps, you can bring your pool back to clear, sparkling blue in just a few days. Here’s how to fix green pool water and keep it from coming back.


Why Your Pool Turns Green


Green water is a classic sign of algae growth - tiny, fast-spreading plants that thrive in warm, poorly sanitized water. When chlorine levels drop too low, algae takes the opportunity to bloom.


Here are the most common causes:


  • Low chlorine or sanitizer levels

  • Unbalanced pH or alkalinity

  • Poor circulation or filtration

  • Dirty filters

  • Monsoon debris or heavy rain introducing contaminants


If you test your water and see little to no chlorine, that’s your confirmation — you’ve got an algae problem, not just cloudy water.


Step-by-Step: How to Clear a Green Pool


1. Test and Balance the Water


Before you start dumping in chemicals, grab a reliable test kit. Check chlorine, pH, and alkalinity levels.


  • Chlorine should read near zero — that’s why algae formed.

  • pH should be slightly low (around 7.2) for shock to work effectively.


Adjust pH first if needed. If your levels are way off, call your local pool professional — severe imbalances can make your chlorine ineffective.


2. Brush the Pool Walls and Floor


Use a pool brush to loosen up algae clinging to surfaces. Pay extra attention to shady corners, steps, and behind ladders - algae loves hiding there.


Brushing breaks up the algae’s outer layer so your chlorine shock can penetrate and kill it more effectively.


3. Shock the Pool


Now it’s time to destroy the algae.


Use pool shock (liquid or granular chlorine) according to the product’s instructions, but for green water, you’ll likely need a triple shock dose.


Run your pool pump continuously for at least 24 hours after shocking. You should start to see the water change from green to cloudy white - that means the algae are dying.


4. Clean or Backwash the Filter


Dead algae will quickly clog your filter, so once your water turns cloudy, it’s time to clean the filter thoroughly.


  • Sand filters: Backwash until the water runs clear.

  • Cartridge filters: Rinse or replace the cartridges.

  • DE filters: Clean and recharge with fresh DE powder.


If you skip this step, dead algae will stay trapped and can cause another bloom.


5. Run the Pump and Keep Brushing


For the next few days, keep the system running at least 12 hours per day. Continue brushing daily and skimming the surface to remove debris.


Once the water clears, retest and balance your chemicals:


  • Chlorine: 1–3 ppm

  • pH: 7.4–7.6

  • Alkalinity: 80–120 ppm

  • Stabilizer (CYA): 30–50 ppm


How to Prevent Green Pool Water in the Future


The best way to fight algae is to stop it before it starts. Here’s how:


  • Keep chlorine levels stable with weekly pool service

  • Brush pool walls regularly

  • Run your pump long enough each day (especially in summer)

  • Clean filters on schedule

  • Shock after heavy use, storms, or pets in the pool


Regular care keeps your pool sparkling and your weekends stress-free.


When to Call a Pool Professional


Green pool water might look intimidating, but with the right steps and a little patience, you can restore your pool to a healthy, swim-ready blue.


If your pool still looks green after a few days, or you’re struggling to keep your chlorine levels up, it’s time to bring in a professional.


At Sunset Pool Care, we help Arizona homeowners clear green water fast with expert testing, chemical balancing, and full equipment inspections.


Call 480-682-7986 to schedule a service visit or request a quote online.



 
 
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