Why Your Pool is Green Even With Correct Salt Levels

It's one of the most baffling problems a saltwater pool owner can face. You’ve tested your salt, and it’s right in the ideal range. Your salt chlorine generator (SWCG) seems to be running fine. Yet, you look out at your pool, and it’s stubbornly, frustratingly green. How is this possible? The key is to understand that **salt is just the ingredient; it's not the sanitizer.** A green pool means one thing: there is not enough active chlorine in the water to kill the algae. This guide will walk you through the real reasons your saltwater pool is green and how to fix the problem for good.

The Root Cause: Not Enough Free Chlorine (FC)

Regardless of the salt level, algae will grow if the Free Chlorine (FC) level is too low. Your salt system's job is to use salt to create FC. If your pool is green, it means one of two things is happening:

1. Your salt system is not producing enough chlorine.
2. Something is consuming the chlorine faster than your system can produce it.

Let's troubleshoot by looking beyond the salt reading and examining the real culprits.

Troubleshooting Step 1: Check Water Chemistry (The Big Three)

Incorrect water balance is the most common reason for ineffective chlorine, even when the salt cell is working.

A. Incorrect pH Level

Problem: If your pH is too high (above 7.8), your chlorine becomes very ineffective. At a pH of 8.0, more than half of your chlorine is "asleep" and unable to sanitize. Since salt systems naturally cause pH to rise, this is a very common issue.

Solution: Test your pH. If it's high, lower it to the 7.2-7.4 range using a pH decreaser like Muriatic Acid or dry acid. Use our pH Adjustment Calculator to determine the correct dosage. Lowering the pH will "wake up" the existing chlorine and make your shock treatment more effective.

B. Low Cyanuric Acid (CYA) / Stabilizer

Problem: For outdoor pools, CYA protects chlorine from the sun. If your CYA level is too low (below 50-60 ppm for a salt pool), the sun will destroy the chlorine as fast as your cell can make it. You'll never be able to build up a sufficient FC level.

Solution: Test your CYA level. If it's low, add stabilizer to bring it into the 60-80 ppm range for saltwater pools. Use our CYA Calculator. Note that CYA takes a few days to dissolve and register on tests.

C. High Phosphates

Problem: Phosphates are algae's favorite food. They can enter your pool from fertilizers, leaves, and even some municipal water sources. If phosphate levels are high (above 500 ppb), they can create an all-you-can-eat buffet for algae, causing blooms that overwhelm your chlorine production.

Solution: Get your water tested for phosphates at a pool store. If the level is high, use a phosphate remover product according to its directions. Removing the food source is a key step in preventing future algae blooms.

Troubleshooting Step 2: Check Your Salt System & Filtration

If your chemistry is balanced, the problem may lie with your equipment.

A. Is Your SWCG Actually Producing Chlorine?

Problem: Your salt system might be running, but is it producing? A dirty or failing salt cell won't generate chlorine, no matter how much salt is in the water.

Solution: First, check your control panel for any error lights like "Low Salt," "No Flow," or "Clean Cell." If you have a "Low Salt" light, don't just add salt—use an independent test kit to verify the salt level first. The most common cause is a dirty cell. Turn off the power, remove the cell, and inspect it for white, flaky calcium deposits. If you see buildup, clean it following our cell cleaning guide. If the cell is old (5+ years) and clean but still not producing chlorine, it may be at the end of its life and need replacement.

B. Is Your Filter Working Correctly?

Problem: A dirty, clogged, or inefficient filter cannot remove dead algae and other debris from the water, making it difficult to clear up a green pool.

Solution: Check your filter pressure. If it's high, your filter needs to be cleaned (backwashed for sand/D.E., or cartridge cleaning). Run your pump 24/7 while you are treating the algae to ensure maximum filtration. If your filter media (sand or cartridges) is old, it may need to be replaced.

The Action Plan: How to Clear Your Green Pool

Once you've diagnosed the potential issues above, here is the step-by-step process to reclaim your pool:

1. Balance Chemistry: Adjust pH to 7.2-7.4 and ensure CYA is in range.
2. Brush Vigorously: Use a good pool brush to scrub all algae off the walls, steps, and floor. This gets the algae into suspension where the chemicals can kill it.
3. Manually Shock the Pool: Do not rely on your salt system's "Super Chlorinate" feature to clear an active algae bloom. It's not powerful enough. You need to manually shock the pool with liquid chlorine or cal-hypo. The goal is to raise the Free Chlorine to a very high level (often 15-20 ppm or higher, depending on your CYA). Use our Pool Shock Calculator to find the correct dosage.
4. Run Your Pump 24/7: Keep the water circulating constantly to filter out the dead algae.
5. Brush and Retest Daily: Brush the pool daily to prevent algae from resettling. Test your Free Chlorine level daily. Do not let it drop below shock level until the water is no longer green. You may need to add more chlorine.
6. Clean Your Filter: Once the water is clear (it may be cloudy blue/white first), clean your filter thoroughly to remove all the dead algae particles.

Remember, a green saltwater pool is rarely a salt problem. It's almost always a chlorine problem caused by an underlying issue with water chemistry or equipment. By troubleshooting systematically, you can identify the root cause and take the right steps to get your pool back to sparkling blue.