What Causes a Green Pool?
Algae. That’s the short answer. When chlorine levels drop, algae spores multiply fast. Warm weather, rain, and poor filtration speed up the process. A pool can turn green in just a few days of neglect.
Common Triggers
- Low chlorine — the #1 cause
- Dirty filter — can’t remove algae spores
- Hot weather — algae loves heat
- Rain runoff — introduces nutrients and dilutes chemicals
- Neglected maintenance — skipping even one week can start algae growth
How to Fix a Green Pool
Here’s the fastest way back to clear water:
1. Shock the pool. Use a heavy chlorine shock treatment to kill algae.
2. Brush walls and floor. Algae clings to surfaces. Brushing loosens it so chlorine can kill it.
3. Run the filter. Keep filtration running 24/7 until water clears.
4. Clean the filter. A clogged filter can’t clear dead algae.
5. Test and balance. After clearing, adjust pH, alkalinity, and stabilizer.
How Long Does It Take?
Light green: 24-48 hours. Dark green or swamp: 3-7 days. Severe cases may need draining and refill.
Is It Safe to Swim?
No. Green water contains bacteria and algae that cause skin irritation, ear infections, and stomach issues. Wait until water is clear and chemistry is balanced.
Prevention: How to Keep Your Pool Clear
The best prevention is weekly pool maintenance. Consistent chemical balancing, filter cleaning, and debris removal stops algae before it starts. Consider a weekly pool service plan to protect your investment.