green pool water

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Green pool water is a common problem for pool owners. Even if you’re doing your best to maintain and care for your swimming pool, green pool water can still occur.

Despite what many pool owners may think, the secret to clean and clear swimming pool water is more complicated than just balancing the chlorine and pH levels. Sometimes that alone just isn’t enough.

Algae thrive in warm, humid environments, so if you’ve recently experienced a change in weather, you’ll need to be diligent about cleaning your pool.

To keep your swimming pool clear of unappealing green pool water you need three elements to be in harmony. The three elements are sanitization, filtration, and circulation.

Pool Sanitization – the chemical requirements for clear pool water

Unless the water has a sufficient level of free chlorine, the correct pH and the correct total alkalinity, algae can grow and cause an unattractive green color. Balancing the pool water chemistry should be the first step when addressing green pool water.

Chlorine is an effective sanitizer for water. When you maintain a swimming pool with the correct amount of chlorine, it will inhibit algae from growing and you’ll circumvent green pool water issues.

Chlorine can also destroy algae that may already exist; you just need to raise the levels. The fastest way to shock is with a main active ingredient of calcium hypochlorite.

When shocking a pool, the goal is to raise your chlorine levels to a point where contaminants such as algae, chloramines and bacteria are destroyed.

I shocked my pool, so why is it still green?

pool chemical balanceFor shocking a swimming pool, the pH should be between 7.2 and 7.6. Shocking a pool with too high pH can cause cloudy pool water. The right range of alkalinity or dissolved salts, that keep the pH stable makes pH and chlorine levels easier to maintain.

There are also some stubborn types of algae that resist chlorine, and you may need an algaecide as well.


Of course, balancing your chemicals won’t help much if your filtration is not managed properly. When addressing green pool water, it’s imperative that you run your filtration system for 24 hours a day once the pool has been shocked.

You may also need to backwash several times a day if you have a sand filter. If you have a cartridge or DE filter, you should be able to clean the filter one time after the water clears.

Green water can quickly clog your pool filter, therefore, you will have to pay special attention to your pool filter until the water clears. You should also make sure that your filter is in working order. A defective filter can cause green pool water.


Often the most overlooked component of pool maintenance is circulation. Algae thrive in stagnant water. Circulating pool water keeps it filtered and clean. It also helps to spread the chemicals added to the water. Pool circulation keeps chemicals mixed and in balance. You may want a pool professional to help you hydraulically balance your circulation system to improve performance.

Ongoing maintenance can prevent green pool water

Once you’ve removed the invasive green annoyance, be sure you test your pool water consistently, preferably once a day. Invest in a good chlorinating system (either a floater, in-line or salt system) to keep an adequate level of chlorine in the pool at all times.

Brush and vacuum the pool at least once a week. Clean your pool filter regularly and upgrade as needed.

Don’t let green pool water or other pool challenges take up your precious free time. View the video below for more information or contact your local  Premier Pool Service to help maintain your pool, so you can spend your time swimming. We offer FREE estimates and peace of mind.

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