Rob is a pool-service industry professional with over 20 years of experience.
Pool is Green but Chlorine is High
If the stabilizer level is too high in a pool, it will lock the chlorine molecules, rendering them ineffective as a sanitizer. This usually happens as a result of using chlorine tablets that contain cyanuric acid. Pools that sanitize the water using salt systems or methods other than tablets usually don't have this problem.
Although you will get a chlorine reading—sometimes a high chlorine reading—your pool may still have algae or other problems. This is because the chlorine molecules are locked up by the high cyanuric acid level.
Dilution Is the Solution
First thing's first. You cannot add chemicals to lower the stabilizer level. Cyanuric acid (a stabilizer) can be added, but to lower it, the pool needs to be diluted with fresh water. There is no chemical on the market that you can add to your pool water to lower the stabilizer.
If you just need help with cleaning a green pool, learn how to properly shock your pool.
What's the Ideal Level for Pool Chlorine Stabilizer?
You should aim for a stabilizer level between 30 and 50ppm. Test the stabilizer or have your water tested and see what the stabilizer level is. Some pool stores list it as either stabilizer or cyanuric acid level.
I service some commercial pools, and the county health inspectors like it below 100ppm, which makes sense because the chlorine is usually very controllable and effective below this level. However, for most homeowners, shoot for 30–50ppm.
How to Dilute Your Pool Water to Lower the Stabilizer Level
Unfortunately, depending on your stabilizer level, and of course, the size of your pool, you are going to have to drain a significant amount of water from the pool. Some customers I have don't like this because of the cost of replacing the water. However, if you don't do this, you will have recurring problems. If you have a cartridge filter, you may want to learn how to clean a cartridge filter. Many problems can be caused by a bad filter.
Drain the Water
Most pool pumps have more than one valve coming to the intake side of the pump. (Skimmer/Main drain) sometimes a third cleaner line. In any case, you need to close the skimmer line and open the drain valve on the return side. (If you don't have a drain valve, have one installed! You'll need it anyway.)
Another option for draining water from the pool would be a submersible pump in which a garden hose can be used as a drain line.
Drain about two feet of water from the pool. Yes, 18-24 inches below the bottom of the tile line.) This is why the skimmer line needs to be closed. Reset the valves and add water from the hose. This can take several hours, depending on the size of the pool and the water pressure from your hose. Let the pool filter on normal cycle and have the stabilizer re-tested. There should be a significant decrease in stabilizer.
You May Also Be Interested In:
- How to get rid of black algae
- Advanced pool water chemistry
resolving issues with pool water when chlorine, pH, and alkalinity are in balance. Why is my pool still getting algae?
- How to turn your swimming pool from green to clean
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
Question: Is there any other way to lower the stabilizer in a swimming pool?
Answer: No. The water needs to be diluted with fresh water. I know that a product came out recently that supposedly lowers stabilizer, but I can say with confidence after trying it, that it doesn't work and it's costly. Calcium hardness is the same way. If it's too high, the water needs to be diluted.
Read More From Dengarden
Question: Why does my chlorine test high? It's orange instead of yellow, but I haven't added chlorine for a week.
Answer: The test reagents are most likely bad. They have a shelf life and can create false readings if they haven't been replaced in a while.
Question: How do you make the stabilizer level in the pool higher?
Answer: Add Stabilizer (cyanauric acid)
Question: Why would pool water turn clothes and skin green/blue?
Answer: This is a water chemistry issue. I recommend having a full parameter chemical test done professionally, including a metals test (Iron and copper).
Question: Do you add the stabilizer chemical to the pool or the water return?
Answer: You will add the stabilizer directly into the skimmer. Stabilizer does not dissolve quickly, so it's not a good idea to put it directly into the pool; however, it will gradually dissolve when added through the skimmer.
Rob Hampton (author) from Port Richey, Florida on April 10, 2020:
Stephen... Yikes! That's quite a jump in CYA after draining and adding fresh water. I suggest having your source water tested, which normally should not have any stabilizer in it. That would be the only explanation for this. CYA should NOT increase after adding fresh water. I have used this product with not so impressive results, but it's out there... https://www.amazon.com/Bio-Active-Products-Stabili...
Stephen mott on April 10, 2020:
I have a vinyl liner in ground pool and my CYA was at 190 so I drained 2 feet of water and filled with fresh and it went up to 250 I did not add any chemicals of any kind during this time what is going on and how do I get my CYA down/
Rob Hampton (author) from Port Richey, Florida on May 06, 2019:
Hi Bill. Dilution will lower the cya level. Rain, a leak in the pool, or just regular evaporation and adding water to the pool.
Bill Muncey on May 06, 2019:
What would make the cyanauris acid to go down in the first place? I could not keep the chlorine level up in my pool until I discovered the stabilizer was low. I've had the pool for over 20 years, first time that ever happened.
Rob Hampton (author) from Port Richey, Florida on October 18, 2018:
Hi Anna, Thanks for reading. You are doing everything correctly to lower the stabilizer level. Re-check the level. If under 100, it should be ok. That said, without being there to test all of the other chemicals, I can offer a few suggestions. The first, and most important being filtration. Make sure there is good flow through the system. Clean the filter often. Run the pump an extended amount of time until pool clears (10 - 12 hours/day). Keep the pH a bit on the low end for now (7.2 - 7.4), chlorine around 5.0 and alkalinity 80 - 100. Have the water tested for phosphates and treat if needed. Even if the chemicals aren't perfectly balanced, I can't stress good filtration enough. If this is an above ground pool with no main drain, point the return DOWN so water shoots toward the bottom of the pool. I hope this helps.
Anna Mifsud on October 18, 2018:
I have been sweeping the pool to waste to reduce stabilizer and topping pool with more water, i have repeated this numerous times but pool is still green.