Where did my cyanuric acid go??

[phonedave]

I wanted to close this thread in case anyone finds it in a search. I added cyanuric acid again and it held. The first time I added it, it was in full sunlight. Which my pool has all day. I think It may have possibly burned off because of the sun?

Nope, sun does not burn off CYA. In fact the problem with CYA is that the only practical way to get rid of it is to do a water change. The right amount of CYA is great, it protects the FC from being burned off by the sun. Too much CYA is bad, it reduces the efficacy of the FC to a point where you need extremely high levels.

Also, CYA, because it is slow to dissolve, takes a while to disperse and show up when testing. After adding what you calculate to be to correct amount of CYA, wait a day or two to make sure it is dispersed before assuming that your calculations were off and you need more.

Secondly the girl at the pool store said to just pour it into my skimmers, so I did. I'm not sure if that matters but the second time I did the sock method. I also waited and did it in the evening when the sun was not shinning directly on the pool. This time I used the Clorox brand from Walmart which was cheaper than what the pool supply store sold me the first time. It worked great. Thanks for all the help. I Love this site!!

CYA is not easy to dissolve, when you dump it into your skimmer, it will often go into dead spots in your filter where there is not enough flow to dissolve it. So it just sits in you filter until you backwash it out. This is why the sock method is recommended. You have found one of the secrets of poll ownership. As long as the chemicals on the label are the same, it does not matter where you buy it, or how much it costs. CYA from the pool store is the same as CYA from Wal-Mart. You may have to watch with bleach, because heat and time can degrade it. So 8% bleach at a store with high turn over may be better than 8% bleach at a store that brought in a trailer full three months ago and has it sitting in the trailer in the sun because the stock room is full.