High Free Chlorine And Cyanuric Acid

[CarlyNJ]

Hi there, having some issue and hope you can help. I have a 15X24 oval above ground pool with a Hayward DE filter and attached chlorinator that we usually put two 3" trichlor tablets in a week, depending on how quickly they dissolve. The pool is in a very sunny spot.

About a week and a half ago we had a ton of rain and when we tested our levels were non-existent (although the pool was and is still crystal clear) and we took a sample to the pool place who had us put in alkalinity increaser and ph increaser, then shock it. Levels were good for about a week after that, and we only got in a few times. We have not shocked it since last week (and we don't usually need to shock it, I think that was the first time we had to since we first got the pool 3 years ago)

Now the pool is still clear, but when we tested yesterday before getting in, the free chlorine is super high (darkest color on test strip which only reads up to 10ppm) and the Cyanuric Acid was also high, at about 150ppm. The rest read in "pool ok" range. Hardness was 250ppm, Total Chlorine was 3ppm, pH was 7.2ppm, total alkalinity was 120ppm. We didn't get in.

We turned off the chlorinator and left it off all day today too, hoping the sun would help break up the free chlorine- and the readings are exactly the same.

Any advice how to get these down? Why is the free chlorine so high but the total is in range? We have a 2 year old and don't want to risk swimming if it's not safe.

Thanks!

Carly

[CarlyNJ]

I wanted to note that I did read that article on the chlorine/cya relationship but it doesn't say how to resolve a continuous high reading. I thought maybe by turning off the chlorinator and letting the sun at it would help break it down, but alas after a full day of sun it did not. Should I give it more time or do I have to get rid of some of the water and will the problem then just keep recurring?

[TXPoolOwner82]

Read this response by waterbear regarding Trichlor and CYA levels: http://www.poolspaforum.com/forum/index.php?showtopic=30118&st=0&p=132498entry132498

"For every 10 ppm FC added by trichlor you are also adding 6 ppm CYA."

He also states that draining it is the only way to remedy the problem of high CYA levels.

[CarlyNJ]

It's hard to interpret that because he's discussing public pools.

2 days now of chlorinator turned off and sunny skies during the day (and it rained hard last night) and still pretty much the same readings, except the total chlorine is now a smidge higher, but still in "ok" range. How can that be? I can understand you can't bring the CYA back down but shouldn't the sun be breaking up the chlorine? Maybe my chlorinator is bad?

[chem geek]

With the CYA at 150 ppm, the chlorine may only drop by around 10% per day. So if it's very high as you indicate, you might not notice the drop without having a FAS-DPD chlorine test. If you want a more rapid drop in chlorine you can use a chlorine neutralizer, but really with that high CYA level you could probably use the pool. Again, with a FAS-DPD test you'd know for sure.

Technically, the Total Chlorine cannot be lower than the Free Chlorine. Possibly the high chlorine level is bleaching out the Total Chlorine test more than the Free Chlorine test for some reason. Again, please get the Taylor K-2006 test kit.

[waterbear]

Free chlorine is reading low because the test is bleaching out because chlorine levels are too high for the test.(it's either DPD or strips and both bleach out at high chlorine levels) total chorine can be tested with OTO which does not bleach out (and the TC test on some strips are cupric OTO based and do not bleach out).

Like chem geek said, get a Taylor K-2006 test kit. It uses FAS-DPD testing for FC and CC and wion't bleach out and read low when it is really high.

You CYA is way too high at 150 ppma and you need to replace some water to get it down or your are going to have problems iwht algae and cloudy water.

Getting your CYA down to a manageable range will silve the problem but the contined use of trichlor iwl cause it to come back. I would suggest learning how to take care of your pool with either liquid chlorine or laundry bleach (same thing. I sent you a PM.