CYA disappeard ove the winter?

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PolareNJ

0
May 21, 2015
45
Hamilton, NJ
We have an inground pool, vinyl liner, approx. 22,500 gallons. Last year we battled both high combined chlorine (which was resolved) and high CYA of 173. We stopped using trichlor tablets and switched to liquid chlorine in August. The last test from the pool store (yes, I know... don't trust it and have ordered a Taylor K-2006 test kit) showed the following readings the day before we closed the pool in late August:

FC = 4.6ppm
CC =0
Alkalinity (w/stabilizer correction) = 139 ppm
pH = 7.7
Cyanuric Acid = 173 ppm
No copper, iron

We were told to drain half the pool and refill to bring down the CYA to an acceptable level. As we thought we would be replacing the liner and would refill with fresh water this spring, we closed the pool. We have not replaced the liner, and have drained and replaced about 500 gallons of water before opening the pool on Monday. Before adding chemicals, the water was tested at the same pool store with the following results:
FC = 0.3
TC = 0.3
pH = 8.5
Alkalinity = 337
Cyanuric Acid = 2 ppm (!)

Obviously, the CYA drop of 171 ppm over the winter seems impossible. Has anyone heard of this before? Could the high alkalinity be masking the CYA? The water temperature is approximately 65 degrees: could this be giving a low CYA reading? After dealing with very high CYA last year, we are very hesitant to adding any stabilizer until we are comfortable that the test results are accurate and won't shoot up later on.. By the way, we are using test strips at home that give a 'low' reading for CYA (<30ppm). We also know that we need to get the FC up, but can't seem to without knowing whether or not to add stabilizer.

Regarding the high Alkalinity/pH reading:
We're not sure the reason for this jump in pH and alkalinity over the winter. In addition to regular closing chemicals, we did have a 'Smart Pool Winter Pill' (enzymes) in the pool over the winter. Could this have caused the higher readings?
We have added 3 gallons of muriatic acid to the pool since opening and using the test strips we now have a pH reading of 7.2, but the alkalinity is still in the 'very high' range. How to get this lower without dropping the pH too much?
The water in the pool is crystal clear for the time being.

Thanks for any advice you can give. I've read through some of this great website for answers, but have not found them yet.
 
Never mind I see it is crystal clear water.

Add some bleach to target 2 ppm for now since your CYA is likely 0

Add Stablizer to a sock and set it in top of the skimmer or tie it in front of your return jet. Target 30 for now until you get your test

You can use PoolMath to figure out how much
 
Welcome to TFP!

You have some wild numbers there, and I would encourage you strongly to get a good kit and some solid numbers. I don't know what's in the smart pill, but TA just doesn't go up on it's own. It's not uncommon for Cya to disappear over winter, especially if the pool gets Green with Algae. The pH you show goes well with the high Alkalinity, but the fluctuations you show are very suspect. It's unfortnuate, but Pool Store readings are really hard to rely on.
 
If your CYA disappeared.... wait, you did let the water mix a while, correct? There's not a layer of snowmelt on top?... it could well have converted into ammonia. You can buy an ammonia test kit at a pet store or tropical fish store, or the pool store might even have the tester. The other way is to wait for your test kit. Add 10 ppm FC to the water and let it mix for half an hour and see what you get. If most of the FC is gone and CC is way up there, you have Ammonia.

If so, the answer is bleach. Lots of it. And when the CC drops off, then you add CYA and worry about the rest.

I'd hold off adding anything but 2 or 3 PPM bleach everyday until you have the test kit in your hands.
 
Thanks, everyone. I was under the (mistaken) impression that CYA never disappeared, but could go down a little. We didn't seem to have any green algae and the pool was only a little cloudy when we opened it and was clear in 2 days. The pool was more frozen than usual during this colder-than-average winter. One last question: once we get the stabilizer in range, would it be OK to use trichlor tablets for a week when we are away? or are we asking for trouble? Again, thanks for the quick feedback.
 
PolareNJ said:
Thanks, everyone. I was under the (mistaken) impression that CYA never disappeared, but could go down a little. We didn't seem to have any green algae and the pool was only a little cloudy when we opened it and was clear in 2 days. The pool was more frozen than usual during this colder-than-average winter. One last question: once we get the stabilizer in range, would it be OK to use trichlor tablets for a week when we are away? or are we asking for trouble? Again, thanks for the quick feedback.
Click to expand...
Just target 40 or 45 so you have room for what the pucks add. A whole lot of us use pucks when we're out of town. You just can't feed a pool a steady diet of 'em and stay troublefree.
 
I can testify that CYA can drop over the summer. Our pool was opened on Tuesday and this is the 7th year in a row we closed at CYA about 60 and opened at negligible amt. We have never appeared to have ammonia.
 

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Getting on the right track: calcium high, monopersulface residual reading, and more.

Just received my new test kit TF-100 and have run two tests over two days to get used to it. Before I get to the results, here is some background: We struggled with high CYA last year (which disappeared over the winter); had to slam the pool last year (58 lbs of calcium hypochlorite); opened the pool to an alkalinity of >350ppm and pH of 8.5 ppm (both pool store tests). Because of the high alkalinity, we added 3 lbs of non-clorine (monopersulfate) 2.5 weeks ago to keep the pool clean while we worked on the alkalinity and before we started our own testing. We have added 5 gallons of muric acid in steps approximately 2 days apart and have been aerating the pool. To increase the cyanuric acid and add chlorine (without increasing calcium) we have been using tricolor tablets. The water is crystal clear, no odors, no stinging eyes, sliminess, etc. We also add algaecide once a week. These are the results from the TF-100 test this morning:
FC = 2 (still a beginner at this: when the water clears, it has turned pinkish again after a few seconds. Should I keep adding reactants?)
CC = 7
pH = 7.2
Alkalinity = 300
CYA < 20
Calcium Hardness = 400
CSI = 0.25

I took a water sample to the store partly to check their numbers against mine, and partly because it seems the monopersulfate is still throwing the chlorine readings after 2.5 weeks (the store uses a strip to check for the monopersulfate levels and our water is showing a 'high' concentration). We added many (15+) bags of monopersulfate last year and I'm wondering if this residual reading is from a build-up over the years? Monopersulfate is supposed to disappear over a few days, but it's not. So now we're showing a very high CC, which may be impacted from the monopersulfate. The FC has been steadily increasing (the store test has it at 0.8 vs. my reading of 2 ppm). Pool store reports CC of 6 vs. my 7ppm. The store test shows CYA of 18, though it's too low to measure on the TF-100. So my questions:

Should we wait out lower monopersulfate readings before trying to slam the pool (that is if we need to)?
If not, how should we go about this? We have liquid chlorine, but how much to use? Would using liquid chlorine get us into more trouble as we have such high calcium already?

Any help is appreciated.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

Greetings NJ! A few comments initially - congrats on the TF-100! Awesome. Keep using it and do not feel obligated to have your readings verified by the pool store. I guarantee your readings are more accurate. As for the pool store products (bags of shock, etc) - stop immediately. Liquid bleach/chlorine is ALL you need. Same goes for algaecides and stuff. They are just taking you money. Maintain the proper FC level (with bleach) and that's all you need. Do not use the tablets anymore either. If you need to increase CYA to your 30-50 range, reply on granule stabilizer. But I suggest checking your CYA in about a week since you've been using other products that have stabilizer in them already. It takes about a week for the CYA levels to adjust in your water. In short - Trust your TF-100. Ask everyone here at TFP if you have a specific test set question. You'll do fine. :)

- - - Updated - - -

As a reminder - review the links in my signature (especially Recommended Levels) to keep you straight. Those links are great tools to have.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

1. The first time the solution goes from pink to completely clear is the endpoint of the test. disregard that it turns to pink again later.

2. The CC's test of 7 ppm is a whopper and I believe it is from the MPS.......I have never seen it hang around for that long and have no clue to it's cause.

3. Per the instructions, did you wipe the dropper tip when you did the TA test? I think the TA is likely not that high.

4. Stop using the tablets and add enough CYA to get to 40-50.

I am really concerned about some of your numbers. 58 lbs of Cal Hypo increased your FC by about 220 ppm. I'm sure those are multiple doses but, Wow, what did your pool look like to require that much FC? Likewise 5 gallons of muriatic?? What are you trying to do, lower your TA (and you are still at 300 ppm TA?

If the mps was put in 2.5 weeks ago, any residual of it has to be long gone but nothing else explains the very high CC's test result.

I would suggest you take things one issue at a time.

Keep your FC at 3 ppm or close to that and add enough CYA to get to 40-50

Once you do that then reduce the TA down to about 110 by following the "how to" article in Pool School.

Report back when your TA target is reached and we'll go to the next step. (keeping your FC at 3-5 ppm all the time.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

Thanks, Dave. Here's some answers to your comments:

During the TA test I have been diligent in wiping the tip after each drop. I also used the alternate method described in the 'extended test kit directions' using 10ml of water to help save reactant.

Regarding the slam last year: the pool looked good, but the CC was so high (in combination with a CYA of 170) that we used that much Cal Hypo over several doses during a very long night.

Regarding the muriatic acid this year: Initially, we needed to get the pH of 8.5 and TA down. Have succeeded with the pH and are still trying to get the TA down, and after the 5 gallons, it's decreased from somewhere around 380 at opening (pool store test) to 300 (TF test) using the Pool school article and aerating to keep pH in check. I would have thought the TA would have moved much more by now. TA was at 184 when we closed the pool last year. Have no idea where all the alkalinity came from over the winter: could it be all the CYA that disappeared over the winter? Pool looks great right now! (see original post above)

Last question: how concerned should I be about the high calcium hardness reading and adding calcium hypochlorite?

Thanks again.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

Your CH is a bit high but within the limits of what we suggest as normal. I would not drive it any higher with Cal-hypo.....it's too easy to use liquid chlorine. Keeping your pH down in the low 7's will minimize any scale risk.

So just keep aerating. Are you dropping your pH down to 7.0, and then redosing when it rioses to 7.8?

CYA and TA are unrelated......TA just seems naturally high.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

We've brought the pH down to 7.2 and then aerate to 7.5, then add more muriatic acid.

Thanks, Dave, for your help. I'm feeling more comfortable now. We'll use the liquid chlorine to get to 3ppm. According to the PoolMath, it looks like we need approx. 40 ounces to begin, and then use a maintenance dose to keep it there until we get the TA down.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

Trying to get the FC up to 3, and using the Pool Math, added 34 oz of liquid chlorine, but this only got me to 2 ppm from 1.5 ppm. Added another 32 oz, but this really didn't move the reading at all. Should I continue to add and then test after a 1/2 hr until I hit the 3 ppm? Or will this end up being a SLAM? CYA seems to be just below 20 ppm and the pool is in the bright sun.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

It sounds like your chlorine is being consumed by some unseen algae in your pool. That is very common. I would suggest two, really three steps.

1. Fight the unseen organics with a bit more chlorine......say keeping it around 5 ppm. Dose that chlorine in the evening after the sun is off the pool ......that will make it most effective.

2. Continue to drop your TA using the acid/aeration method in Pool School as you have been. 120 would be a good goal and should be pretty doable. Because you indicate your precision with the testing and the principles involved, I am going to suggest you actually drop the pH down to 6.8 before you begin to aerate back up to the high 7's. This will make things happen noticeably faster.

3. Once your TA is down, SLAM the pool. Follow the article in Pool School precisely. That should take care of that algae still in there and you will be about all set for a troublefree summer.
 
Re: Getting on the right track: calcium high, monopersulface residual reading, and m

Thanks. According to Pool Math, I should add about 57 oz to get to 5 ppm. Should I test 1/2 hr. after adding? If I don't get to 5 ppm, should just add more (how much?) and then wait another 1/2 hr to test again? Just trying to get this right.

I'm looking forward to that troublefree summer
 

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