Why Does My Florida Pool Keep Turning Green ? 5 Common Causes

If you've ever looked at your pool and wondered, "Why is my pool turning green again?", you're not alone.

A green pool is usually a sign that algae has found conditions that allow it to grow. Simply adding chemicals may clear the water temporarily, but if the underlying problem isn't corrected, the green water can come right back.

After years of working on Florida swimming pools, we've found that recurring algae problems usually come down to one or more of five things:

1. The water chemistry isn't properly balanced.

2. There isn't enough effective sanitization.

3. The water isn't circulating properly.

4. The pool equipment isn't operating correctly or isn't running long enough.

5. Phosphates or other nutrients are helping support algae growth.

Let's look at each one.

1. The Pool Chemistry Isn't Properly Balanced

Water chemistry is the first place to look when a pool begins turning green.

A pool needs an appropriate sanitizer level, along with properly managed pH and other water-balance factors. If the sanitizer isn't able to do its job effectively, algae can gain a foothold.

Florida pools can be particularly demanding because of heat, sunlight, rain and frequent environmental exposure.

The important point is:

Don't just add chemicals because the water looks green. Test the water first.

Testing gives you information about what is actually happening in the pool instead of guessing at the problem.

Your water chemistry should be evaluated and adjusted according to the pool type, sanitizer system and current conditions.

2. There Isn't Enough Sanitization

A pool can have water that looks reasonably clean and still be heading toward an algae problem.

If the sanitizer level drops too low, algae can begin to grow. Heavy rain, high temperatures, pool use, debris and other environmental factors can all increase the demand on a pool's sanitizer.

Saltwater pools aren't exempt from this problem.

A saltwater chlorine generator produces chlorine, but it still depends on the equipment operating correctly and the pool being maintained properly.

If a pool repeatedly loses its sanitizer level, don't simply keep adding more chlorine. Find out why the pool isn't maintaining an adequate sanitizer level.

That could lead you back to water chemistry, circulation, filtration or equipment.

3. Poor Circulation Can Create Problems

Good circulation is one of the most overlooked parts of pool maintenance.

Your pool may have plenty of water moving through the system, but that doesn't necessarily mean every part of the pool is circulating properly.

Poor circulation can leave areas where debris, contaminants and algae have a better opportunity to accumulate.

Pool return jets should be positioned to encourage good overall water movement rather than simply creating an attractive pattern on the surface.

This is also why keeping the filter clean and the circulation system operating properly is important.

Water that doesn't move properly can become a problem.

4. Equipment Problems — or Not Enough Run Time

Sometimes the chemistry isn't the real problem.

A pump may not be operating correctly. A filter may be restricted. A valve may be incorrectly positioned. A salt system may not be producing chlorine as it should.

Or the equipment may simply not be operating for enough time to provide the circulation and filtration the pool needs.

If a pool is repeatedly turning green despite apparently reasonable chemical maintenance, the equipment deserves attention.

Look for signs such as:

• Weak water flow from the return jets

• A filter pressure reading that is higher than normal

• Air entering the circulation system

• A pump that isn't running properly

• A salt system that isn't producing chlorine as expected

• A filter that becomes dirty or restricted quickly

A problem with circulation or filtration can contribute to the return of algae even after the pool has been treated.

5. Phosphates Can Help Feed Algae Growth

Phosphates are another factor worth considering when algae keeps returning.

Phosphates can enter swimming pools from a variety of environmental sources, including fertilizers and organic material. They can serve as a nutrient source for algae.

But there's an important distinction here:

Finding phosphates doesn't necessarily mean you've found the entire problem.

A pool can contain phosphates without turning green.

The bigger question is whether the pool also has conditions that allow algae to grow — such as inadequate sanitization, poor circulation or other maintenance problems.

That's why we prefer to look at the entire pool rather than automatically treating one test result.

Why Does My Pool Keep Turning Green After I Just Cleaned It?

This is one of the most frustrating situations for a pool owner.

You clean the pool, add chemicals, get the water looking good again — and a few days later, it's starting to turn green.

When that happens, it's worth stepping back and asking:

What allowed the algae to come back?

Was the sanitizer being maintained?

Was the pool circulating properly?

Was the filter becoming restricted?

Was the pump operating correctly?

Was the pool getting enough circulation time?

Was there an underlying equipment problem?

Could environmental conditions or nutrients be contributing?

Treating the visible algae is only part of the job.

Finding the reason it keeps returning is the important part.

What Should You Do If Your Pool Is Green?

Start with the basics:

1. Test the pool water.

2. Check the circulation and water flow.

3. Inspect the filter and equipment.

4. Make sure the sanitizer system is operating correctly.

5. Remove leaves, vegetation and other debris.

6. Look for obvious equipment or circulation problems.

7. Treat the algae according to the pool's condition and the manufacturer's directions for the products being used.

8. Continue monitoring the water after it clears.

If the problem keeps returning, don't just keep adding chemicals.

There may be an equipment, filtration, circulation or water-balance issue that needs to be identified.

When It's Time to Call a Pool Professional

Some green pools are straightforward maintenance problems.

Others aren't.

If you've corrected the water chemistry and the pool continues to turn green, or if you're seeing equipment problems, poor circulation, unusual filter pressure or persistent water-quality problems, it's worth having the entire system evaluated.

At Monkey Rock Pools, we've spent years working on Florida swimming pools and troubleshooting the problems that cause water-quality issues to come back.

Sometimes the solution isn't another chemical. It's finding out what is causing the problem in the first place.

Need Help With a Green Pool?

If your pool keeps turning green and you're tired of treating the same problem over and over, Monkey Rock Pools can help diagnose the underlying problem and get your pool back on track.

Contact Monkey Rock Pools for professional pool service and maintenance in the North Pinellas area.

Coming next:
Why Won't My Pool Hold Chlorine?

That article will take a closer look at one of the most common reasons a pool repeatedly develops algae problems.

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