From: stormreaver
Written: 2018-07-11 16:37:07.20854
Subject: Pool Chemistry Blues

I've had my above-ground pool for several years, and it has usually been a monstrous battle to keep the water clean and clear. Up until now, there have been exactly two years where I managed to beat back the inevitable algae infestation.

For years, I have bought sodium hypochlorite chlorine tablets to keep my pool sanitized. Sodium Hypochlorite tablets contain stabilizer, which prevents the chlorine from burning off in the sunlight. This sounds great to the novice pool maintainer, as chlorine tablets aren't necessarily cheap.

I had learned everything I needed to know about pool water balance: chlorine at one to three parts per million (which never worked for me, by the way, so I kept it at 10 to 12), PH at 6.8 to 7.6 (I usually kept it at about 7.2), total alkalinity between 80 and 120 (mine usually averaged 90). I thought to myself, smugly, that those so-called pool specialists sites are always wrong, since their chlorine recommendation never worked for me. I have found empirically that they don't know what they're talking about (or so I thought).

There was another chemical factor that appeared in most balance help requests: CYA, which I found meant Cyanuric Acid. I briefly read about it, but didn't understand it, so I concluded that it was useless. More on this later.

For two total, non-consecutive years, I managed to keep my pool water clean and clear. On those years, I proudly proclaimed to my wife that I had mastered pooled chemistry, despite those so-called pool water expert Web sites. For all the other years, I fought with mild depression at my inability to keep my pool water clean. For those years, I ended up draining and refilling my 13,000-gallon pool two or three times during the swimming season.

This year, I once again found my pool quickly turning swamp-water green. I did more research on the same pool water sites I had been disparaging, and once again saw people posting their Cyanuric Acid levels along with their other water statistics. This time, I spent more time reading up on Cyanuric Acid, and I saw, for the first time, the role of CYA in algae formation in a form I could understand.

When Cyanuric Acid levels are high, chlorine effectiveness goes way down. When CYA levels reach a certain height (80-something), chlorine becomes almost entirely ineffective. I rushed out to my pool, and performed a CYA test: 90.

AHA! Yay! I found the problem. So now, which chemical do I use to lower CYA, I asked Google. I was dismayed to find that there is no chemical that lowers CYA. The only way to lower it is to partially (or even fully) drain the water and replace it with fresh water.

Damn! It costs about forty five dollars in water to fill my pool, and I desperately didn't want to do that. However, I found that every site with an opinion on CYA said the same thing: drain and refill. So I did.

I didn't drain it completely, but mostly. There was still algae in the approximately three inches of water left in my pool, but I assumed that it would be overwhelmed by the large volume of clean water I was putting into the pool. It turns out I was wrong. By the time the pool was full again, the water was still very green. My wife and I were in near crisis now. We just wasted nearly fifty dollars in water costs for absolutely no gain! I was depressed, but I soldiered on.

I performed another CYA test with the remainder of my testing reagent, and it was about 20 parts per million. I then found the crucial missing link to my problem: the Sodium Hypochlorite tablets I had been liberally adding to my skimmer contained Cyanuric Acid! I had no idea for all these years. Having discovered that, I realized that the tablets had worked great until the CYA accumulated in my pool over time. Each tablet added approximately 0.6 parts per million of CYA. CYA causes issues with no only chlorine, but also with PH and alkalinity. My pool water quickly fell into crisis over and over again.

I also discovered that Calcium Hypochlorite does not contain stabilizer (which is what CYA is called). With that new knowledge, I went to Walmart and picked up a 6-pack of Calcium Hypochlorite shock, and put all 6 bags into my pool that night (to prevent day-time chlorine burnoff), and left my filter running. Remember that at this point, my pool was a green swamp again.

By the morning time, there was no difference in water quality. I was somewhat concerned, but remembered reading that it could take a few days for the shock to do its job. So I left the filter running all day while I went to work. When I got home, the water was neither any better or any worse. I was getting more depressed about my pool, but I left the filter running anyway.

When I got up the next morning, I found that all the green was gone! The water was still cloudy, but now it was cloudy blue instead of an impenetrable green. I backwashed and rinsed the filter, then put it back into its normal filtering mode and went to work. When I came back home, the cloudiness was substantially reduced! I could now faintly see the bottom of my pool again!

However, my PH was VERY high (higher than 8, I think), and my alkalinity was on the low side (80); so I added about half a gallon of Muriatic Acid to lower the PH to a bit lower than 6.8, and then added a couple pounds of baking soda to raise both the PH and the alkalinity to acceptable ranges (7.1 and 90, respectively).

When I came home from work the next day, the pool water was still blue, but now the bottom of the pool was readily visible. My chlorine levels were off the chart, so I told my family to stay out of the pool until the chlorine came way down. That happened the next morning, so I told them that the pool was safe for swimming. The water was nearly perfectly clear and clean!

So the moral of this story is to never dismiss Cyanuric Acid as inconsequential. It is an equally important part of pool chemistry as chlorine, alkalinity, and PH. Too much CYA makes all the other readings useless.
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