Green water in the pool - causes, what to do, removal

Green water in the pool – causes: why is the water in the pool green?

The green color appears when the formation of green water outpaces disinfection. The most common culprits are:

• Algae (chlorophyll): They reproduce intensively already at 0.2 mg Fe/l of leaf fertilizer and temperatures > 24 °C. How to react? Shock chlorination + algaecide.
• Metals (iron, copper): They oxidize, forming green complex compounds. How to react? Flocculant + filtration.
• pH of water outside 7.0–7.4: Chlorine weakens ↔ algae grow. How to react? pH minus or pH plus.
• Poor circulation / UV: Dead zones, heat, and light = spa for algae. How to react? Extend filtration to 24.h.

Transparent → slightly milky → yellowish-green → bottle green

The journey from crystal clear water to green soup sometimes takes just 48 hours.

The water in the pool is turning green – warning signals

• Matte, "powdery" shade of the surface
• The phenomenon of green water on a microscale: whitish deposits near the nozzles
• Slippery film or tiles along the waterline
• Milky cloudiness in the evening after a sunny day

Green water in the pool after filling – initial errors

• Well water: Risk of highiron levels, algae in the biofilm. Recommended product: Flocculant + filtration 48 h.
• Tap water: Risk of low residual chlorine and poor buffering capacity. Recommended product: pH minus or pH plus, 1 kg/10 m³.
• Water from a tanker: No quality data available. Recommended product: Complete starter kit (shock chlorine + algaecide).

Green water inpool after rain – impact of precipitation

Acid rain (pH ≈ 5.5) sharply lowers pH and deactivates free chlorine, while pollen and dust increase contamination in pool water. After every heavy rain:

1. Check pH and free chlorine.
2. Use shock chlorine (10 g/1 m³).
3. Run filtration for at least 12 hours continuously.

Green sediment at the bottomcheck.

ryzach.

Above-ground pool vs. frame pool – differences

• Garden (masonry): greater thermal inertia, sand filter, dosing automation.
• Frame: small volume, cartridge inserts; requires more frequent micro-doses of chemicals.

Green water in the pool after chlorine – when disinfection fails

The phenomenon of "chlor lock" involves the binding of chlorine in chloramines, making the purification of pool water seem ineffective.

• pH: Ideally 7.0 – 7.4. Critically > 7.6.
• TAC (alkalinity): Ideally 80 – 120 mg CaCO₃/l.Critically < 60.
• ORP: Ideally > 650 mV. Critically < 550.

How to clear green water in the pool after shocking with chlorine

Check-list 0–24 h
0 h – measure pH, adjust.
1 h – add 15 g/1 m³ shock chlorine.
2 h – start continuous filtration.
6 h – vacuumbottom.
12 h – add flocculant in the skimmer.
24 h – ORP control; if < 650 mV, repeat.

Key thought: How to clean a pool from green water in a nutshell – always finish the stage with a measurement, because chlorinating pool water without tests is like "shooting" with your eyes closed :)

Cloudy water in the pool – home remedies

• 50 g of baking soda/1 m³ – increases alkalinity
• Vitamin C tablet – reduces metal stains
• Nylon sock for outlet – fine dust filter
• Pool chemicals: polymer flocculant 100 ml/10 m³
• 1 ml/1 m³ of special preparation for clarifying pool water

Solution for green pool water – plan__24 h

Green water in the pool - what to do? Pool water maintenance should start with testing pH and free chlorine, and then:

1. pH adjustment → 7.2.
2. Chlor shock.
3. Polymer algaecide.
4. Flocculant.
5. Filtration 24/7.

What to do about green water in the pool?

It's worth remembering: Pool green water treatment = polymer algaecide (10 ml/1 m³), supported by continuous pool water filtration non-stop.

How to eliminate green water in the pool

1. Brush the walls and bottom.
2. Vacuum to the drain (release the wastewater, not through
3. Perform backwash – reverse flow of clean water through the sand filter.
4. Replace ⅓ of the volume to eliminate green water and dilute phosphates.

Ways to deal with green water in the pool – comparison

• Chemistry – chlorine + algaecide + pH minus or plus.
  • Effectiveness: Very high.
  • Cost: Low.
  • Maintenance: Testing every 2 days.
• UV-C Lamp 16-55 W.
  • Effectiveness: High.
  • Cost: Medium.
  • Maintenance: Bulb replacement annually.
• Ozonator 0.5 g/h.
  • Effectiveness: High.
  • Cost: High.
  • Maintenance: Service every 6 months.

Parameter Monitoring – prevent the pool water from turning green

Regular testing guarantees clean pool water and lower chemical usage:

• water pH:
  • Optimal: 7.2 – 7.4.
  • Minimum: 7.0.
  • Maximum: 7.6.
• Free chlorine:
  • Optimal: 0.6 – 1.0 mg/l.
  • Minimum: 0.3 mg/l.
  • Maximum: 3 mg/l.
• Cyanuric Acid (CYA):
  • Optimal: 30 – 50 mg/l.
  • Minimum: 10 mg/l.
  • Maximum: 70 mg/l.

ORP Sensors vs. Test Strips

• ORP: automation, accuracy ± 5 mV, expenditure ≥ 400 PLN; great forworked.
• Strips: cheap (0.80 zł/piece), reading in 30 seconds; require regular discipline. For an amateur pool, a combo of strips + manual adjustments is sufficient.

Author - water treatment specialist MaciejWaliduda