Why Is My Pool Green? 5 Causes and How to Fix Each

You step outside on a Saturday morning, coffee in hand, ready to enjoy the pool — and the water is green. Maybe it is a pale, milky green. Maybe it looks like a swamp. Either way, your weekend plans just changed.

A green pool is not just ugly. It is unsanitary. Green water means algae is growing, and algae creates the perfect environment for bacteria, mosquitoes, and other things you definitely do not want your family swimming in.

The good news? Every green pool can be fixed. I am Corey Adams, owner of Peachy Pools, and over 15 years of servicing pools in Kennesaw, Marietta, and throughout Cobb, Paulding, and Cherokee counties, I have recovered hundreds of green pools — from light tints to full-blown swamps. In this guide I am going to walk you through the five most common causes and exactly how to fix each one.

If you want the complete step-by-step recovery process, check out our Green Pool Recovery Guide. For a deep dive into the different kinds of algae you might be dealing with, see Types of Pool Algae.

1. Low or Zero Chlorine

This is the number one reason pools turn green, and it is especially common here in Georgia. When summer air temperatures push past 90 degrees — and pool water temperatures climb into the high 80s or above — chlorine gets consumed at an incredible rate. The sun's UV rays break down free chlorine, and warm water accelerates algae growth. It is a one-two punch.

If you are a salt pool owner, your salt chlorine generator may not be keeping up with demand. Many homeowners set the generator's output percentage in April and never touch it again. By July the pool needs significantly more chlorine than it did in spring, and the generator simply cannot produce enough. The same thing happens with tablet feeders — a three-tablet setting in May might need to be five or six tablets in August.

Vacation neglect is another huge contributor. You leave for a week at the beach, and nobody is checking the pool. A week of unchecked Georgia summer heat is more than enough time for algae to take hold and turn the entire pool green.

How to fix it

Test your water immediately. If free chlorine is at or near zero, you need to shock the pool — not with a maintenance dose, but a full superchlorination to at least 20–30 ppm of free chlorine. Use liquid chlorine (sodium hypochlorite) for the fastest results. Make sure your cyanuric acid (CYA) level is between 30 and 50 ppm so the sun does not immediately destroy the chlorine you just added. Run the pump 24/7 until the water clears.

2. Pump Failure or Insufficient Run Time

Your pool pump is the heart of the entire system. It pulls water through the skimmer and main drain, pushes it through the filter, and sends treated water back into the pool. If the pump is not running, nothing else matters — the chlorine sits stagnant, the filter cannot do its job, and algae gets exactly the still, warm water it loves.

I see this all the time: a breaker trips during a summer thunderstorm, and the homeowner does not realize the pump has been off for three days. Georgia storms can be intense — heavy rain dumps organic debris into the pool, the wind knocks branches and leaves everywhere, and then the power flickers. By the time you notice the pump is off, the pool is already turning.

Variable-speed pump owners sometimes run into a different version of this problem. To save on electricity, they set the pump to its lowest speed and shortest run time. That can work fine in the cooler months, but during a Georgia summer you need to turn the water over at least once every 8–10 hours. If your pump speed is too low to achieve that, the water in the far corners of the pool is essentially sitting still.

How to fix it

First, verify the pump is actually running. Check the breaker, check the timer, and listen for the motor. If the pump runs but sounds labored or the flow rate is weak, the impeller may be clogged or the capacitor may be failing — both common issues. During summer months in Georgia, run the pump a minimum of 10–12 hours a day. If you have a variable-speed pump, increase the RPM until you can feel strong flow from every return jet in the pool.

3. Poor Water Circulation and Dead Spots

Even if your pump is running and your chlorine level looks fine at the test strip, you can still get green patches if the water is not circulating evenly throughout the entire pool. Algae loves still water. It will establish itself first in the areas with the least movement — behind ladders, on steps, along the waterline in corners, and on the floor of deep ends where return jets do not reach.

After big Georgia storms, skimmer baskets fill up with leaves, pine straw, and pollen almost overnight. A clogged skimmer basket chokes off water flow to the pump, which reduces overall circulation even though the pump itself is fine. The same goes for a pump strainer basket packed with debris.

I tell every customer the same thing: point your return jets so they create a gentle clockwise rotation across the surface of the pool, and angle at least one jet downward toward the deep end floor. This keeps the entire volume of water moving and prevents the dead spots where algae loves to start.

How to fix it

Empty your skimmer and pump baskets. Adjust return jet eyeballs so they all push water in the same rotational direction — not straight up, not pointed at the wall. Brush the walls, steps, and floor thoroughly. Brushing disrupts algae's grip on surfaces and suspends it in the water column where the chlorine can kill it and the filter can capture it. For a complete guide on keeping your chemistry and circulation dialed in, read our Pool Water Chemistry Guide.

4. High Phosphate and Nutrient Levels

Chlorine kills algae, but phosphates and other nutrients feed it. Think of it this way: if chlorine is the brake pedal, phosphates are the gas pedal. Even if you are maintaining a decent chlorine level, extremely high phosphate levels give algae so much food that it can outpace the chlorine's ability to kill it.

Here in Georgia, phosphate loading is a year-round challenge. In spring, pine pollen coats everything — including your pool. Pollen is packed with phosphorus. In summer, lawn fertilizers wash into pools during heavy afternoon thunderstorms (and we get plenty of those). In fall, decaying leaves sink to the bottom and release nutrients as they break down. Even well-maintained pools in Kennesaw, Marietta, and the surrounding areas constantly battle organic nutrient input just because of the environment.

How to fix it

Have your phosphate levels tested — most standard test strips do not include phosphates, so you may need a dedicated phosphate test kit or a professional water analysis. If phosphates are above 300 ppb, use a phosphate remover product to bring them down. More importantly, address the source: keep landscaping fertilizer away from the pool deck, skim leaves and debris daily during heavy pollen season, and rinse off before swimming. A good skimmer sock or fine-mesh skimmer basket helps catch pollen before it dissolves.

5. Filter Problems

Your filter is the last line of defense. After the chlorine kills algae cells, the filter is what actually removes them from the water. If the filter is dirty, clogged, damaged, or undersized, dead algae and debris stay suspended in the water — keeping it cloudy or green even after you have shocked it.

Cartridge filters are the most common type I see in residential pools across Cobb and Paulding counties. They work well, but they have to be cleaned regularly. During summer or during a green pool recovery, I recommend pulling the cartridge out and hosing it down every few days — not every few weeks. A cartridge that is coated in algae sludge has almost zero filtering capacity.

Sand filters are low maintenance most of the year, but the sand media wears out over time. If your sand filter is more than five years old and you have never changed the sand, the grains have likely become smooth and rounded, which means they cannot trap fine particles effectively. A sand change can make a dramatic difference in water clarity.

DE (diatomaceous earth) filters provide the finest filtration available, but they have internal grids that can tear. A torn grid allows water to bypass the DE coating entirely, which means you are essentially running unfiltered water back into the pool.

How to fix it

Clean or backwash your filter before you begin the recovery process and again every 12–24 hours during the recovery. Check the filter pressure gauge — if it is 8–10 PSI above your clean starting pressure, the filter needs attention right now. Inspect cartridge elements for tears or permanent discoloration that will not rinse off (that means it is time for a replacement). For sand filters, consider a media change if it has been more than five years.

The Green Pool Recovery Process

Once you have identified the root cause, here is the general process I follow for every green pool recovery. I have used this same approach on hundreds of pools across Cherokee, Cobb, and Paulding counties, and it works every time — no shortcuts.

Why Green Pools Are So Common in Georgia

If you have lived in Georgia for any amount of time, you know our summers are brutal. Air temperatures regularly exceed 95 degrees from June through August, and pool water temperatures can climb into the low 90s. That kind of heat is a paradise for algae — it accelerates growth rates dramatically.

Add in our afternoon thunderstorms (which dump rain, fertilizer runoff, and debris into pools), the massive pine pollen season in March and April, and the general humidity that keeps everything damp and organic-matter-rich, and you have the perfect recipe for a green pool. I have been servicing pools in Kennesaw, Marietta, Dallas, Acworth, Canton, and Woodstock for over 15 years, and I can tell you that green pools are not a sign of a bad pool owner — they are a sign of living in Georgia.

The most common scenario I see is vacation neglect. A family leaves for a week or two during the summer, nobody checks the pool, and they come home to a swamp. The second most common is a storm knocking out power — the pump goes off, the chlorine burns away in the heat, and by the time the power comes back, the algae has already bloomed.

When to Call a Professional

A light green pool that just started turning? With the right products and this guide, most handy homeowners can handle it. But if the water is dark green, black-green, or if you can see visible algae growth on the walls and floor, it is time to call in a professional. The amount of chlorine, the constant filter cleaning, and the multi-day process involved can be overwhelming — and if you get the dosing wrong, you waste time and money while the algae digs in deeper.

At Peachy Pools, I handle every green pool recovery personally. No random technicians, no guesswork. I test the water, determine the exact treatment plan, and come back as many times as needed until the pool is crystal clear. If you are in Cobb, Paulding, or Cherokee County and your pool has turned green, give me a call or request a free estimate. I have seen every shade of green there is, and I know how to fix every single one.

Want to prevent this from happening in the first place? Our Pool Water Chemistry Guide covers everything you need to know about maintaining proper chlorine levels, balancing your water, and keeping algae from ever getting a foothold. And if you would rather leave the weekly maintenance to someone who has been doing it for over 15 years, check out our Pool Maintenance Guide for Georgia to see what professional weekly service includes.