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Why Is My Pool Green? Fixing Murky Water

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There are few things as refreshing as taking a swim in a sparkling pool on a hot day. Unfortunately, it’s not always easy to keep your pool looking fresh. Green pool water is a major turnoff. Instead of feeling fresh and inviting, it feels loathsome. Just the look of the water makes your skin crawl. If you dare take a swim in the murky water, you’ll just want to take a shower immediately because you’re left feeling dirty. Even though green pool water is an obvious turnoff, it’s not always easy to fix. You might have found yourself wondering on multiple occasions “why is my pool water green and how can I fix the issue?”. The good news is that even the greenest pool water can be cleared again.

Why Is My Pool Green? Reasons for Green Pool Water

Green pool water is most often a result of chemical imbalances in the pool. Balancing the amount of chlorine in pool water is especially important. If your pool contains either too much or too little chlorine, there’s a good chance you’ll end up with murky, green pool water.

The Importance of Chlorine

The purpose of chlorine in swimming pools is basically to keep the water clean. Chlorine is commonly used to clean water – even drinking water.

Chlorine is a popular choice as an anti-septic in water. That’s because it kills basically anything in the water that’s alive. From harmful bacteria to just about any kind of algae, chlorine kills it all!

Of course, this is also why a chlorine imbalance in your pool can lead to problems. When you use too little chlorine, algae starts to grow freely in your pool water, causing the water to appear green and murky.

How to Fix Green Pool Water?

Even though a chlorine imbalance is one of the most common reasons for pools green pool water, the color of your pool can reveal a lot about what the underlying problem is.

Fixing Light Green Pool Water

Most pool owners start to notice something is wrong when the color of their pool turns a light green. At first the color may seem almost normal – not entirely off-putting. However, even light green pool water indicates a low level al algae in the pool water.

A pool shock is the best way to treat light green pool water before the problem worsens.

Fixing Medium to Dark Green Pool Water

The darker the green of your pool, the more algae is present in the water. So, in cases where pool water is a medium to dark green color, there’s more algae present in the water than if it were light green.

Once again, a good pool shock should help to clear up your problem.

Fixing Black-green Pool Water

By the time your pool reaches this level of algae, it might start to look more like an over-sized frog pond that an actual pool. In some cases, depending on how bad the problem is, a proper pool shock may still work.

What’s important is to allow the filter to run at all times (although you’ll probably have to replace your filters once the water is clear again).

That said, there are cases when the overgrowth of algae in a pool is simply too bad to fix. When this happens, the pool water will have to be drained and cleaned out properly before filling it up again. This is a job best suited for pool maintenance professionals to handle.

How Too Much Chlorine Turns Your Pool Green

Why Is My Pool Green: Metal OxidationAt this point you might be asking yourself, why is my pool green even if I add more chlorine than recommended?

Surprisingly enough, too much chlorine can also cause your pool water to discolor, but no algae can grow in water with high chlorine levels.

The reason why your pool might turn green, even if you add a ton of chlorine, is because the chlorine can oxidize metals in the pool water, such as copper, iron, silver or manganese.

Copper is especially prone to cause this. If you’ve ever seen an old copper statue, you’ll know they tend to turn a blueish green color – this is actually caused by the copper oxidizing over time.

When chlorine oxidizes metals in your pool water, the same thing happens, they turn greener, which leads to the discoloration.

Then main difference between light green water caused by algae and light green water caused by metals oxidizing is the cloudiness or brightness of the water. Water with algae always appears a bit cloudy and murky. You might even notice some algae growing on the sides of your pool – a sure sign you’re dealing with an algae problem.

Water with oxidized metals, on the other hand, will be bright and almost appear luminescent in photographs at times. Although the color can vary from a very bright green to a khaki green or even a dark apple green, you won’t see algae growing anywhere on the sides and the water probably won’t look too cloudy.

How Fix Discolored Pool Water from Oxidation?

Different metals turn different colors when oxidized. As you know, iron rusts when oxidized, causing it to become a reddish brown color.

Some of the most common reasons for green pool water that’s caused by oxidation include:

  • Using pool chemicals that contain copper and metals
  • Filling your pool with water that’s naturally high in metals
  • Using metal pipes, like copper pipes, for your pool system

The best way to deal with metal oxidation is to use less chlorine in your pool. If you’re able to swap out metal piping or pool chemicals with ones that are metal-free, that would also help.

Testing the Langlier Saturation Index of your pool water can also be helpful. If your pool water is corrosive, meaning it “eats away” at things, it’s more likely to pick up metals by corroding pipes, fixtures and more. Balancing the LSI can help you maintain less corrosive pool water that won’t pick up metals as easily.

Maintain A Balanced Pool pH

Maintaining an optimal pool pH can also help combat green pool water. That’s because the pH level of your pool water can affect the efficacy of chlorine. If the pH of your pool is too low, chlorine will dissipate rapidly. This can lead to algae growth as well as discoloration caused by oxidation of metals.

If the pH of your pool is too high, the chlorine will lose its power to combat algae and kill off germs.

The ideal pool pH is approximately 7.4-7.6, although anywhere between 7.2-7.8 is considered acceptable.

Why Is My Pool Green After Rain?

A lot of pool owners struggle with pools that turn green after rain. This happens as a result of the rain water diluting your pool chemicals and disturbing the delicate chemical balance. When your pool water is diluted, there’s less chlorine to fight off algae. Rain water can also disturb the pH balance of your pool water.

The best way to prevent your pool from discoloring because of rain storms is to keep it covered. This should block rainwater from coming into your pool and disrupting the balance of chemicals.

If your water is already green from a rain storm, simply add some chlorine, clean away any debris in the water and run your filter to clear up your pool again. In some cases, a pool that’s discolored from rain might need to be shocked.


Pool water chemistry can be delicate to maintain. If you’re struggling with green pool water, it could be caused by anything from an imbalanced pool pH, to how much chlorine you’re using.

By simply maintaining your pool pH and using chlorine correctly, you should be able to rectify your green pool water. The general cleanliness of you pool also plays a factor, so be sure to run your pump and filter the water.

Joseph FernandezWhy Is My Pool Green? Fixing Murky Water

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