High Cynaric Acid

by Rick Vaughan
(Foristell Mo. )

My pool is a 26,000 gallon above ground vinyl liner. around 7/31/2014 the cya raised to 113 and then my water started clouding up.

8/5/2014 stopped chlorinating and started shocking using 1 pound shock each time so not to overshock. Also drained water down to bottom of skimmer and refilled(on a well so have to be careful overworking well pump.). did this 3 or 4 times from then through 8/13/2014.

Following are readings I got from pool store(my test kit has ran out of reagents. New taylor test kit you recommend has been ordered.)

8/5/14 free chlorine 1.45 total chlorine 1.63
ph 7.8 calcium hardness 379 total alkalinity 118 cya 106 shocked added 2 1/2 lbs ph minus. 8/12/2014 free chlorine .78 total chlorine 1.00 ph 8.0 calcium hardness 381 total alkalinity 113 cya 104 iron .1 added 2 1/2 pounds ph minus then shocked again this time 2 pounds shock.

8/13/2014 noticed green on pool steps and in auto cleaner filter bag. shocked again 1 pound. 8/14/2014 free chlorine 1.62 total chlorine 1.84 ph 7.8 calcium hardness 378 total alkalinity 119 cya 100 iron 0.1 phosphates 200.

All above numbers are from wonderful pool chemical sales people. On 8/18/2014 I decided to draw down the pool 1/2. But only drew it down 18" Then started refilling. The pool is now filled to about 1 inch below the skimmer. Takes a while running water for an hour and letting well pump rest for 2 hours(recommended by well people). Borrowed friends test kit only can test the following chlorine 5.0 ph 8.0 alkalinity 140.

Now after this long winded writing my question is what in your opinion can I do to be able to safely swim this week end (100 degree forecast plus party that's been scheduled for months) thanks for any help Rick Vaughan

Thanks for the question Rick

The most important thing you can do right now is to get the CYA down to around 30ppm and a partial drain and refill is your best option. There's no chemical to reduce the CYA.

The reason the pool went cloudy is fairly simple. It has to do with a combination of a high pH and high CYA. pH range is 7.2 - 7.8. When it gets 8.0 and over you're only using about 25% of the available chlorine. The CYA range is 30 - 50ppm. Yours is high so that's rendering the chlorine less effective. The CYA coupled with the high pH and you're fighting a losing battle.

What you're doing right now is the best thing, a partial drain and refill. My advice would be to get the CYA to 30ppm and the pH down to 7.0 to prepare the pool for shocking. It's 20 oz. of acid to reduce the pH 0.2 per 10K gallons.

The FIRST thing is to get the CYA to 30ppm BEFORE you do anything else. If you start shocking and adding acid you're wasting money and chemicals because you need to drain and refill. Once you reach the 30ppm mark it'll be time to adjust the pH.

I'd start with about 40 oz. of acid in a large bucket filled with pool water, stir and broadcast around the perimeter, sweep, FILTER for 10 hours, retest and make another adjustment if needed.

Next is to shock the pool. It's 1 gallon of chlorine to increase the FC 10ppm per 10k gallons. You have a 26k gallon pool so you're going to use 3 gallons of chlorine. Make the adjustment in the same manner as the pH adjustment. Don't use granular chlorine as this will not only raise the CH but raise the pH as well. Calcium hypo has a pH of 12.

Shocking is a process, not an event. The trick is to get AND keep the chlorine above 10 - 12ppm for a period of time. You'll need to manually dose the pool with chlorine to keep it at 10 - 12ppm. Make the adjustment at night, then retest in the morning. Be sure to have the pump running 24/7 and backwash once per day. You can go up to 15ppm, but no higher. Anything after that and you're wasting money and chemicals.

At the very end you can use a clarifier to help with the cloudiness. It's 5 oz. per 5k gallons for maintenance but go up to 10 oz. for clearing up the pool. The slightly higher TA will come down when you decrease the pH. The range for TA is 80 - 100ppm.

This is a fairly simple fix and should only take a few days to clear up. If it's done right you're looking at around $40 - $50 in chemicals.

I hope this has answered your question to your satisfaction.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Cyanuric Acid (CYA)" category.

Check back to this post for updates or answers.

If you feel your situation is more complex and want immediate assistance (within 24 hrs) you can make a donation of your choice and I'll answer your questions by phone.

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Have a great Summer.


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Rising levels of cyanuric acid

by Karen wilkins

Hi, hope you can help. I have a small outdoor pool with a jet to swim against. At the start of the season I had to empty it because the level of cyanuric acid was too high and now I can see it rising again. I use a chlorine for outdoor pools which contains cyanuric acid as a stabiliser, however, I realised that I keep the cover on most of the time so in effect the environment in the water is more like an indoor pool as its not constantly exposed to the sun.

So, I'm thinking of alternating between using my normal chlorine and calcium hydrochlorite instead. Do you think this will work and are there any problems involved in switching between 2 products.

We don't have hard water and the ph tends to be low and I have to raise it regularly so these shouldn't be a problem.

Hi Karen. Once you get your CYA to the right level of 30 - 50 ppm there's no reason to add any kind of stabilized chlorine unless it decreases. You should only need to use liquid bleach which is the exact same thing as pool chlorine for your weekly maintenance.

No need to switch back and forth. Keep it simple. Get the CYA in the right range then use bleach to maintain the FC of 2 - 4 ppm.


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