Your Pool Went Green Overnight. Here's Why — and What to Do.
You walked outside this morning, looked at your pool, and it's green. Not a little hazy — green. That sinking feeling is valid. A green pool isn't just an eyesore. It's a sign that algae has taken over, your chlorine has crashed, and your water is no longer safe to swim in.
The good news: it's fixable. The key is moving fast — because in Houston heat, algae doubles every few hours. Here's exactly what's happening and what to do about it.
Why Do Pools Turn Green?
Three things combine to cause a green pool: algae spores (always present in outdoor air and water), depleted chlorine, and heat. Houston is basically a perfect algae incubator — high temperatures, humidity, and intense UV light all destroy chlorine faster than in cooler climates.
When your free chlorine drops below 1 ppm, algae seizes the opportunity. A bloom that starts as a slight green tint on Tuesday can be a completely opaque swamp by Thursday. Heavy rain, a missed chemical dose, or a malfunctioning feeder are the most common triggers.
Can You Fix It Yourself?
Honest answer: it depends on how bad it is. If you caught it early — water is slightly green or teal but you can still see the bottom — a DIY shock treatment might work. Slam the pool with a heavy chlorine shock dose (triple-shocking overnight), brush every surface, run the pump continuously, and retest in 24 hours.
If the pool is fully opaque and you cannot see the floor, stop. You're dealing with a full algae bloom, and a DIY treatment will most likely fall short. Without the right shock dosing calculation, commercial-grade algaecide, and professional vacuuming equipment, you'll spend a week and several hundred dollars and still end up calling a pro. Skip ahead.
What the Professional Green Pool Process Looks Like
When Radiant Pools arrives for a green pool call, here's what happens:
- Water test: We measure your current chemical levels — pH, alkalinity, cyanuric acid, phosphates, and free chlorine — to calculate the exact shock dose needed.
- Heavy shock treatment: We add the correct amount of liquid or granular chlorine shock to overwhelm and kill the algae colony. No guessing.
- Algaecide application: A commercial-grade algaecide is added to prevent regrowth during treatment.
- Brushing all surfaces: Algae clings to walls, steps, and floor grout. Every surface is manually brushed to break it loose and expose it to the shock.
- Extended pump run: The pump runs continuously — minimum 24 hours — to circulate treated water through the filter.
- Vacuuming dead algae: Once the algae dies (it turns grey or white), we vacuum the dead material out of the pool. This is critical — leaving it in will consume your chlorine again.
- Retest and balance: A final water test confirms your chemistry is correct: pH 7.4–7.6, alkalinity 80–120 ppm, chlorine 2–4 ppm. Done.
How Fast Can It Be Fixed?
It depends on severity:
- Light green (mild bloom): 24–48 hours after treatment, your water should be clear.
- Dark green or black (severe bloom): 3–5 days for full clearing, sometimes requiring a second shock treatment and filter cleaning mid-process.
Every day you wait, the algae grows. Calling same-day isn't overreacting — it's the right call.
Need Same-Day Green Pool Cleanup in Houston?
Radiant Pools offers emergency green pool service across the Houston metro. We'll assess, treat, and get your pool back to swim-ready as fast as possible. Don't wait — algae doesn't.
Call Now: (713) 487-9687Or get a free quote at radiantpoolstx.com/contact
Common Question
Is it safe to swim in a green pool?
No — not under any circumstances. A green pool contains active algae colonies and, more dangerously, the conditions that allow harmful bacteria including E. coli and other pathogens to thrive. With chlorine at near-zero, there is nothing protecting swimmers from infection. Keep everyone — including pets — out of the pool until it has been treated, cleared, and retested.