It's a frustrating moment for any pool owner: you pull back the cover, ready for a swim and find cloudy, green water instead. It’s a common issue in Perth, especially after heavy rain or a stretch of warm, sunny days. A green pool doesn’t just ruin the mood; it means your water is unbalanced and unsafe to swim in.
The good news? Fixing it is completely doable. With the right approach (and a bit of patience), you can restore your pool to the sparkling backyard oasis you love.
Let’s break down exactly how to fix a green pool and how to prevent it from happening again.
What Causes a Pool to Turn Green?
If your pool water is green and murky, algae is the likely culprit. Algae spores are constantly entering your pool from rain, wind, dust and even swimmers. When water conditions are off, these spores quickly take over.
Here are the most common causes:
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Low chlorine levels: Anything below 1.5 ppm creates the perfect breeding ground.
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Unbalanced water: If pH, alkalinity or hardness levels are off, chlorine becomes ineffective.
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Poor filtration: A clogged or underperforming filter cannot keep algae under control.
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Environmental factors: Heat, rain, debris, and diluted chemicals all increase risk.
Step-by-Step: How to Fix a Green Pool
The best approach is a multi-stage treatment process that addresses both the cause and the clean-up. Here’s how to do it right.
1. Prep the Pool
Start by removing everything from the water, including automatic cleaners, pool toys, and ladders. Empty the skimmer and pump baskets to allow proper flow, and use a leaf rake to scoop out as much visible debris as possible.
Top up the water so it reaches about three-quarters of the way up the skimmer box, then adjust your filter settings.
If you have a sand filter, set the multiport valve to recirculate.
For cartridge filters, remove the cartridge and seal the lid.
This setup allows the chemicals to circulate freely and prevents the filter from trapping them.
2. Treat the Water
Begin by shocking the pool with liquid chlorine. Use 10 litres for every 10,000 litres of pool water and pour it slowly around the pool edge. This strong dose helps destroy algae and oxidise contaminants.
Next, add a specialised algaecide (250ml per 10,000 litres). This is particularly effective for tougher algae strains. Follow up with a flocculant at the same dose. This will help bind the dead algae particles so they can sink to the floor.
Then, thoroughly brush the walls and floor of your pool to loosen algae from surfaces. This helps the chlorine and algaecide reach every corner. Run your pump for one to three hours to circulate the chemicals evenly.
3. Let Everything Settle
Once the chemicals are fully circulated, turn the pump off. Leave the water completely still for 12 to 36 hours. During this time, dead algae and fine debris will settle on the pool floor, forming a visible layer of sediment with clear water above.
4. Vacuum to Waste
Now for the clean-up. Use a manual vacuum to remove the settled debris from the floor. If you have a sand filter, set your valve to waste. For cartridge filters, use a discharge hose or bypass to remove water directly.
Vacuum slowly and carefully. Moving too fast will stir up the sediment and delay the process. If you disturb it, wait for it to settle again before you finish. Keep an eye on the water level and top it up as needed throughout.
5. Final Clean and Rebalance
After vacuuming, give your filter a thorough cleaning. For sand filters, perform a long backwash and rinse. For cartridge filters, hose down the cartridge before reinstalling it.
Return your system to normal filter mode and run it continuously for 24 to 48 hours. This will help remove any remaining fine particles.
Finally, bring a water sample to your local pool professional. They’ll test and rebalance your water chemistry, ensuring it’s safe, comfortable, and crystal clear.
Want to make sure you don’t miss a step? Download our Green Pool Recovery Checklist to keep this process simple, organised, and stress-free.
How to Prevent a Green Pool
Preventing algae is far easier than removing it. Regular maintenance is your best defence.
Here’s what to stay on top of:
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Maintain chlorine between 1.5 and 3.0 ppm
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Keep pH levels between 7.2 and 7.6
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Run your pump for 8 to 12 hours daily
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Clean your filter regularly
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Skim out leaves and debris often
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Test your water weekly, especially after rain or heavy use
Let Pool Assist Take Care of It
If you're not sure how to fix a green pool, or simply don't have the time, Pool Assist is here to help. Our licensed technicians specialise in green pool recovery across Perth, using proven methods to restore clarity and balance fast. We also offer regular servicing plans to keep your pool clean, safe, and swim-ready year-round.
From expert chemical balancing to hands-on equipment support, we make pool ownership easy. Get in touch with our team today, or visit us in-store to explore our full range of products and professional pool services.
Note: This post was originally published on July 25, 2022 and has been updated on October 29, 2025.