My Naked Pool Went Green After Rain: Step-by-Step Fix

Heavy rain can turn even a well-maintained Naked freshwater pool green almost overnight. Here is exactly why it happens and what to do — step by step.

Why Does Rain Turn a Naked Pool Green?

Rain disrupts the Naked system's balance in four ways:

• Dilutes copper levels — copper is your primary algaecide. Rainwater brings it below the 0.2 ppm threshold where algae can survive.
• Lowers pH and alkalinity — rain is slightly acidic (pH ~5.6). This shifts your water chemistry out of range.
• Introduces nutrients — dust, pollen, leaf debris, and phosphates wash into the pool. Phosphates are algae food.
• Adds algae spores — rain carries airborne spores directly into the water.

The result: copper drops below effective levels while algae gets a fresh supply of food. That is why your pool turns green fast.

Step-by-Step Fix

Follow these steps in order. Most Naked pools clear within 2–5 days.

Step 1: Remove Debris

• Skim leaves, twigs, and floating debris immediately.
• Empty skimmer baskets — organic matter feeds algae.
• If debris has settled, vacuum to waste if possible.

Step 2: Brush All Surfaces

• Brush walls, floor, steps, and corners thoroughly.
• Algae clings to surfaces. Brushing breaks it loose so the filter and sanitiser can do their job.
• Repeat daily until water clears.

Step 3: Run the Pump 24/7

• Set your pump to run continuously until water is clear.
• Your Naked system needs circulation to sanitise effectively.
• Clean or backwash the filter before starting — a dirty filter cannot clear green water.

Step 4: Test Your Water

Use test strips or a liquid kit. Focus on these parameters:

Enter your results into the [Pool Calculator](/) for instant dosing advice tailored to your pool size.

Step 5: Balance pH First

Rain is slightly acidic, so pH typically drops after heavy rain — but it can also read high depending on your water. Either way, pH must be in range before copper can work effectively.

If pH is below 7.2 (most common after rain):

• Add sodium bicarbonate (buffer/baking soda) to raise pH and alkalinity together.
• Dissolve in a bucket of pool water before adding.
• 200g raises TA by ~10 ppm per 10,000L — retest after 4–6 hours.

Read: How to Raise Pool pH →

If pH is above 7.6 (copper cannot kill algae at this level):

• Add liquid hydrochloric acid (muriatic acid).
• Dose slowly into the deep end with the pump running.
• Max 500ml at a time. Retest after 4–6 hours.
• Never add acid with swimmers in the pool.

Read: How to Lower Pool pH →

Step 6: Check and Raise Copper if Needed

If copper is below 0.2 ppm, your Naked system cannot fight algae.

• Run your Naked unit on boost mode (higher output) to produce more copper ions.
• Boost mode typically runs at 2x normal output — check your controller manual.
• Retest copper after 24 hours of continuous operation.
• Do not add copper algaecide — the Naked system produces its own.

Naked Pools Support → for help with boost mode settings on your specific unit.

Step 7: Lower Phosphates (If Above 0.2 ppm)

Phosphates won't stop copper from working, but they feed algae — so even after copper and pH are corrected, algae will return quickly if phosphates remain high. Deal with phosphates once pH and copper are corrected.

If your phosphate test reads above 0.2 ppm:

• Use a phosphate remover (e.g., Lo-Chlor Starver, Pool Perfect Phosfree).
• Add according to the label based on your pool volume.
• Phosphate removers are safe for Naked systems — they do not interfere with ionisation.

Step 8: Retest and Repeat

• Retest pH, copper, and phosphates after 24–48 hours.
• If water is still green, repeat Steps 4–7.
• Continue running pump and brushing daily.

Most Naked pools clear within 2–5 days with this process. If it takes longer, take a water sample to your local pool shop for a full analysis.

Prevention: Avoid Green Pools After Future Rain

The single best defence: keep copper at 0.3+ ppm at all times. When copper is in range, algae cannot establish — even after heavy rain.

Related Reading

• [Fresh Water, Low Chemicals: Your Guide to Naked System Chemistry →](/blog/fresh-water-low-chemicals-naked-system-chemistry)
• [Pool Algae Types Explained →](/blog/pool-algae-types-explained)
• [Freshwater Pool Ready for Summer: 10-Step Naked System Checklist →](/blog/freshwater-pool-ready-for-summer)
• [Pool Test Strip Results Explained →](/blog/pool-test-strip-results-explained)

Calculate Your Fix

Enter your test strip results into our free calculator for personalised dosing advice.

Use Pool Calculator →

*PoolCalculator.com.au is not affiliated with Naked Pools. For official troubleshooting, visit Naked Pools Support →*