Did I inadvertantly discover a way to drop CYA???


Active member
Jun 19, 2007
Charleston, SC
A few days ago I performed the Ascorbic Acid cleaning on my pool. Before the test, I made sure my chlorine was at ZERO. Also, my pH was roughly 7.8 and ALK was around 150-200. The main thing I have had to deal with all summer though is that my CYA has been over 100. Anyway, on with the Ascorbic acid cleaning. I ended up using 3lbs. of acid (mainly because i'm impatient and not sure what i was doing) for my ~10000 gallon pool and about 20 oz. of Jacks Magic The Blue Stuff Metal Solution Too. I was trying to follow Mbar's instructions. Well, the past couple of days, I have been slowing bringing my pH and chlorine back up, using borax and bleach. My pH now reads about 6.8. Alk is around 150. Free CL is reading 1.0 while combined CL shows about 3.0. The biggest shocker of all though was when i tested CYA. I was hoping it dropped a little bit after all of this, but I couldn't believe that it reads 0 - yes ZERO! I would've done the test twice, but i don't have enough Stabilizer Solution left. I know i did it right though - I've performed this test several times this summer. My pool water has a nice green tint because of the new algae growth on the walls and floor - I haven't vacuumed yet - but the water itself is very clear when I do the CYA test. I can fill the test tube to the rim and still see the black dot at the bottom. Does anyone have ANY explanation for all of this? I would say that I might need to add CYA now, but i'm still skeptical! FYI, i'm using the Aqua-Chem 6-Way Professional Test Kit from Wal-Mart.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
If you are holding any FC across a day of sunlight then your CYA level isn't anywhere near zero. I think something must have gone wrong with the test. There is no way I can imagine that the ascorbic acid treatment would bring the CYA down.


LifeTime Supporter
Apr 24, 2007
Ashland PA
If you have a FC of 1 & CC of 3, then you have a TC of 4, Is that correct? That means with the cc chlorine that high, you have may have some organic stuff that ate away the cya. I know that when I open in the spring after having the pool closed, the cya is usually 0. Or you can have a test that is bad. :? Before adding any cya, I would get the water tested at a pool store for cya, because you need to know the level of cya so you can see what level you need to take your chlorine up to shock level :wink: Once you know your cya level, you will need to take the chlorine up to kill the algae. You don't want to get stains back though, so add the chlorine up slowly, looking for stains. If you see stains, get the ph back down to 7 - 7.2, and add more sequestering agent. Add the bleach to take it up to shock level, continuing to add sequesterer if stains are forming. You will have to take it up to shock and hold it there until you can hold a free chlorine level overnight. Let me know if you have any other questions.