Kermit the Frog nailed it when he said it’s no fun being green, and that’s especially true if you’re a pool owner staring at an unusable, avocado-colored swimming hole.
Unlike Kermit, you don’t have to live with it, though. You can go from green to clean in 12 steps without having to drain your pool and start from scratch.
From testing water chemistry and cleaning filters to shocking, brushing, and clarifying your pool water, we’ll explain which chemicals work best, how to properly adjust pH levels for maximum effectiveness, and the professional techniques that can save you money on repairs.
| Project difficulty: Moderate; chemical involved Estimated time to complete: 2 to 7 days, depending on severity Project cost: $50-$150 for chemicals and supplies |
What You Need
- Test kit or strips: Comprehensive kit that measures chlorine (free and combined), pH, alkalinity, calcium hardness, and cyanuric acid levels.
- Pool shock: Calcium hypochlorite is good for standard pools, and dichlor is better for saltwater pools.
- Algaecide: These types of chemicals work with your chlorine to kill algae and prevent regrowth.
- pH adjuster: Common adjusters are muriatic acid or soda ash to raise or lower pH levels in pools.
- Alkalinity adjuster: Basic baking soda raises alkalinity, while muriatic acid lowers it.
- Pool clarifier: Optional product that helps clear cloudy water by clumping tiny particles together so your filter can catch them.
- Filter cleaner: Use this to remove oils, organic matter, and mineral buildup from your filters.
- Salt cell cleaner: For saltwater pools only, this removes calcium buildup from salt chlorinator cells.
| My tip: Use a commercial salt cell cleaner instead of muriatic acid, which can damage the cell’s delicate plates and shorten your cell’s lifespan. |
- Pool brush: Nylon bristles for vinyl pools, stainless steel for concrete or plaster pools.
- Pool vacuum: Manual or automatic, this will get debris, dead algae, and whatever else has settled to the bottom of your pool.
- Skimmer: Standard skimming net to grab floating debris.
- Filter media: New cartridges, fresh DE (Diatomaceous earth) powder, or sand, depending on your filter type.
Steps to Clean a Green Pool
Step 1. Remove Debris
All that stuff floating around your pool isn’t going to help and could be a large source of your murky water problem. Skipping this step will definitely make the whole process take longer.
- Skim the surface to remove anything you can see floating around.
- Vacuum anything that has settled at the bottom.
- Clean out the skimmer and pump baskets so they’re ready to go.
Step 2. Clean the Filter
If your pool is grungy-looking, your poor filter is probably clogged and working overtime, so start fresh with clean or new filters:
- For cartridge filters: Soak the cartridges in the filter cleaning solution as per the package instructions. Rinse thoroughly and allow it to dry before putting it back in place.
- For sand filters: Turn the valve to backwash and rinse until the water runs clear.
- For DE filters: Backwash and add fresh Diatomaceous earth powder if needed.
| My tip: Filters that are cleaned regularly will last longer, but watch for tears or cracks in the cartridge, high pressure in the system, caked-on sand, or a broken manifold, and staining that can reduce how well the whole thing works. |
Step 3: Scrub the Pool
While time-consuming, this is a very important step as it loosens algae from surfaces. Algae are opportunistic. As an admittedly lazy pool owner, I have previously skimped on this. The algae lingered and mocked me from wherever I had missed a spot, so get in there with your pool brush and give it a good scrub down.
- Thoroughly brush walls, floor, steps, and ladders.
- Focus on getting into the corners and crevices where algae hides.
- Brush toward the main drain to help it remove the crud a little faster.
Step 4: Test the Water
Use your test kit to measure the levels in your green pool to figure out first what went wrong. Record the levels as your baseline to compare them after treatments. For a detailed explanation of how to test water, see our guide ”How to Test Pool Water.”
Pool Levels and Green Pools
| Chemical | Ideal Range | Green Pool Connection |
| Free Chlorine (FC) | 1-3 ppm | Low: Not enough sanitizer |
| Combined Chlorine (CC) | Below 0.5 ppm | High: Too many contaminants |
| pH Level | 7.2-7.6 | High: Limits chlorine’s ability to work |
| Total Alkalinity (TA) | 80-120 ppm | Imbalanced: Causes pH to drift |
| Cyanuric Acid (CYA) | 30-80 ppm | High: Lacks chlorine, making it ineffective |
| Calcium Hardness (CH) | 200-400 ppm | Affects the overall water balance |
Step 5. Adjust pH and Alkalinity
For your chlorine to effectively kill algae, it needs your pH and alkalinity levels to be in balance. Adjust the alkalinity first, as it acts as a buffer that will help your overall levels. Follow your product directions for how much to use:
Adjust alkalinity first: Bring total alkalinity to 80-120 ppm
- To raise alkalinity by 10 ppm in a 10,000-gallon pool: Add approximately 1.5 pounds of sodium bicarbonate (baking soda)..
- To lower alkalinity by 10 ppm in a 10,000-gallon pool, add approximately 1.6 cups of muriatic acid (31.45% strength) OR add 2 pounds of sodium bisulfate (dry acid)
Then adjust pH: The ideal level is 7.4, but 7.2 to 7.6 is in your safe range
- To raise pH, add 6 oz of soda ash to raise pH by 0.2.
- To lower the pH, add 12 oz of muriatic acid to lower it by the same amount of 0.2.
If you need a hand adjusting your pH levels, check out “How to Raise Your Pool’s pH” or “How to Lower Your Pool’s pH”
Step 6. Shock the Pool
Now for the magic trick: obliterate the algae with a big dose of chlorine. You can use shock in fresh and saltwater pools, but always check that it’s appropriate for your system and follow dosing instructions. Sometimes, less is more because it’s easier to add more shock than to take out excess.
- Calculate the amount of shock you need based on pool volume and the manufacturer’s instructions on the product.
- Dissolve the shock, if you’re using the granular kind, in a bucket of pool water first. Liquid can typically be added directly to the pool. Always add shock to water, never add water to shock chemicals.
- Add the shock solution around the perimeter of the pool during the evening to prevent sunlight from degrading the chlorine before it can work.
If you’re new to the pool shocking game or just need a refresher, check out “How to Shock a Pool” for more info.
| My tip: When using liquid shock, understand it’s basically industrial-strength bleach and it will stain everything from your clothes to your pool liner, so handle it with care. |
Step 7. Run the Filtration System
You’ll get faster results if you keep the water moving after adding the shock. You may be tempted to save electricity with shorter run times, but it will extend how long it takes to make the pool swim-ready again.
- Run the filter 24/7 until the pool clears, to remove dead algae. Good circulation prevents dead spots where the algae can regrow.
- Clean or backwash the filter daily, if needed, as the algae can clog your freshly cleaned filters, depending on how green your pool is.
- Create good water flow by pointing return jets to create a gentle, circular motion in the pool. Check your skimmers for clogs and that they’re working properly.
Step 8. Add Algaecide
Wait 8 to 12 hours after shocking to introduce the algaecide. This helps prevent regrowth, improves the effectiveness of the shock, and will continue to work for days after to help kill any remaining algae.
- Choose your algaecide carefully, because they are not all created equal. Select one specifically for green algae, and the severity of your green pool problem.
- Follow the directions and add only the amount suggested by the manufacturer.
- Be patient and let the product work. You may see a change in a few hours but If you had a large algae bloom, it can take 24 to 48 hours for results to show up and you may need to rebrush to loosen up stubborn areas so the filter can grab it.
| My tip: Adding algaecide when it’s hot and windy can slow down how fast it works. Here in West Texas, I know. High temps break down the chemicals and help the algae with warmer water. Plus, high winds make the water evaporate faster, messing with your overall balance. |
Step 9. Brush it Again
Yes, more brushing. I know it’s a workout, but it’s what you gotta do to get rid of the tough stuff. Wait about 24 hours after shocking, thoroughly brush the entire pool again to remove any dying algae still clinging to your pool surfaces.
Step 10. Test and Rebalance
We’re in the homestretch, and the end is in sight! Wait 48 hours after you’ve shocked the pool, and re-test the water chemistry.
- Check all levels are within their designated safety ranges.
- Adjust as needed to ensure chlorine, pH, and alkalinity are where they need to be.
- Repeat shock if your pool is still green, but at a lower dose.
Step 11. Vacuum to Waste (If Possible)
If your filter system has a “waste” mode option, you can turn it on to remove debris directly from the pool and bypass your filter to prevent clogging. Vacuum slowly to avoid stirring up the debris, and add fresh water as needed to bring it back up to your fill line.
If you don’t have this option, you can try one of the following:
- Use a manual vacuum connected to a garden hose to bypass the filter.
- Vacuum on regular filter setting, but clean or backwash your filter frequently while you go.
- Consider renting a submersible pump with a discharge hose for severe cases.
- Disconnect the return line on sand and DE filters that don’t have a waste setting. You can usually direct it to where you want the wastewater to flow.
Step 12. Add Clarifier (optional)
The final touch to bring your murky lagoon back to a crystal clear oasis is to add a clarifier. This will help the filter capture any remaining microscopic debris floating around that’s making your pool water cloudy.
- Choose your product. As they essentially all do the same things, you do have options between standard clarifiers, natural enzyme-based products, concentrated formulas, and flocculants.
- Follow the manufacturer’s dosage recommendations and avoid pouring directly into your skimmers. For extreme cases, you may need a second dose after 24 hours.
- Run your pump for 24 to 48 hours to clear out the contaminants. Some clarifiers may cause foaming, but it’s normal and will go away. Clean the filters if the pressure increases in your system, and you’re done!
Troubleshooting Common Problems
A few issues may pop up when cleaning a green pool. Here are the most common problems you may encounter and their solutions:
Pool is Green, But Chlorine is High
Sometimes your chlorine levels are normal or high, but your pool is still green. Here’s why this can happen and what to do:
- Too much stabilizer: If your cyanuric acid (CYA) is above 80 ppm, it can lock up the chlorine and prevent it from working.
How to fix: Partially drain the pool and replenish with fresh water.
- Metals in the water: Copper and iron can come in from well water.
How to fix: Test your pool water for metals and if needed use a metal treatment product from your local pool supplier.
- Overwhelmed chlorine: Sometimes there’s so much algae that it uses up chlorine faster than normal.
How to fix: If all else fails, you may need to repeat the shock process to clear the pool.
Persistent Algae Issues
If algae keeps returning despite your best efforts, try one of the following fixes:
- Check circulation: Inspect your pump and filter system for damage, clogs, or system failures. If there isn’t enough movement in the water, algae can hide in “dead spots” and grow.
- Inspect for biofilm: Look for slimy, sticky buildup in pipes and equipment where algae can hide. Use a biofilm remover to purge it from your system.
- Test phosphate levels: Algae feed off of phosphate. Levels higher than 1000 ppb (parts per billion) lead to blooms. There are phosphate reducers, but the best medicine is to thoroughly clean the pool.
| My tip: If your testing kit doesn’t let you check things like phosphate levels, often your local pool supplier will test a sample for you for free in the store. |
Cloudy Water After Treatment
If you managed to clear the green but the water is still cloudy and dirty-looking, there are some options:
Prevention: The Best Cure
Spending three days scrubbing and de-greening my pool once was enough for me. As Ben Franklin once famously said, an ounce of prevention is worth a pound of cure – or chlorine, in our case. Learn how to stay out.
FAQ: Green Pool Water
No, baking soda (sodium bicarbonate) alone won’t clear a green pool. It raises alkalinity and slightly raises pH, which helps chlorine, but it won’t kill the algae. You’ll still need to treat with sanitizer and algacide.
No, even a slightly green pool suggests algae are present, which can be a haven for bacteria and other pathogens. Plus, the chemicals used to treat algae, like high shock levels, are not safe to swim in. Wait until the water is clear and all the chemical levels are balanced.
From Green to Clean
Transforming your green pool back to its original pristine glory doesn’t have to be overwhelming. By following the steps listed above, carefully testing, thoroughly cleaning, and adding appropriate chemicals at the right time, you’ll be diving into the deep end in no time.
While most pool owners can successfully tackle a green pool on their own, don’t hesitate to call a pro if you get stuck. It can save time, money, and your summer.
Home Gnome delivers the best home service experience at the click of a button. Book reliable, skilled pool cleaning services and leave the rest to us.
Main Photo Credit: Janice Higgins / Adobe Stock
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