Is dry stabilizer salvageable after getting wet?

[jmb]

We just opened our large 36,000 gallon pool. Pool opening test results were
FC 0
pH 7.2
Total Alkalinity 80
CYA 0
Pool temperature 70 F

I expected our CYA to be on the low side but not 0. It ran low all last summer and was 35 when we closed the pool in September. We have to drain the pool below the returns to close so CYA is lower when we open in the pool for the summer. We are added 3.5 kg of dry stabilizer using the using the sock method which per Pool Math will raise our CYA by 26 ppm. I subsequently read that likely if the CYA is under 20 it may show as 0. I am concerned now that if the CYA was perhaps at 15 or so then I may be adding too much dry stabilizer at once.
Last summer we had very good success with keeping the CYA close to 30 ppm .
In retrospect I feel that we should have likely added 2 kg dry stabilizer and then retested before adding more. I am wondering if I remove one of the socks (as the stabilizer has not yet dissolved) will it be salvageable? will I be able to add it back in later if needed? ; or will it turn into a brick when I remove the sock? do I just discard it? and, if so how?; is it safe to put in the garbage? If I can use it later is there a way I should store it? I feel I should add the dry stabilizer at a slower pace and retest. I can buy fresh dry stabilizer if we need to add more later.

I believe we also added too much liquid chlorine at 10.8 as we are getting bleaching when doing the DPD test Bleaching When Doing a DPD Test. Based on the pool opening results I posted how much liquid chlorine should I add to start with? We follow the SLAM method when opening the pool but in the past I have always had enough CYA to follow the Chlorine /CYA chart for slamming. I will try the test again tomorrow morning and hope that some of the chlorine will have dissipated.
The bottom of the pool had a layer of sand/dirt which has been vacuumed away; the water is a bit cloudy but not too bad. It does not look like we will have any algae issues.

I would appreciate your thoughts re removing one of the socks and re how much liquid chlorine to add when CYA is less than 20; as well as any other thoughts you may have re how to proceed form here. Thank you.

 

[mgtfp]

Seeing CYA and FC both at zero always rings and alarm bell. With FC at zero it can happen that certain soil bacteria turn CYA into ammonia.

Ammonia is not good in a pool, it creates a massive chlorine demand:

Ammonia - Further Reading

www.troublefreepool.com

Next step should be to rule that out. To do that you need to calculate with PoolMath how much liquid chlorine you have to add to raise FC to 10ppm. You let that mix in with the pump running. After 30 min you test your FC. If FC is at or close to zero, then you have likely ammonia in your pool, and you have to remove it by following the process in above link. You basically have to add lots and lots of chlorine, until all the ammonia has been oxidised by chlorine, and FC starts to hold when adding liquid chlorine.

Then you can add more CYA and adjust the pool chemistry again.

 

[mgtfp]

And which FC test are you doing? FAS/DPD (powder + drops) or just DPD (powder only)?

Wondering if you are not seeing bleaching of the test but really no FC at all.

 

[mgtfp]

About your sock: you could put it into a bucket of fresh water and keep dissolving it in there.

If your pool turns out to have ammonia, I'd discard the sock, as bacteria will be feasting on the CYA.

If you have no ammonia and need more CYA, then pour the bucket into the pool and finish dissolving the CYA in the sock in your pool

 

[jmb]

For testing the chlorine we are using both the basic chlorine test with the R-0600 and the FAS/DPD powder and + drops. Sorry, I should have mentioned that the 0 free chlorine was right when we opened the pool before we added any liquid chlorine. I was testing the pH and the alkalinity before adding chlorine so we could move to the slam process. We started the pool motor and pump and added 10 Liters of liquid chlorine at 10.8% ; I am not sure how long we waited but I think at least 2 hours; when we tested using the basic test again it was showing some chlorine but still very low; ie .5 to 1 the lowest 2 bars on the scale. We added another 10 Liters (which I now realize was more than we should have. Several hours later we wanted to do the FAS/DPD test with drops. We first repeated the basic test and this time it was at 5 on the basic test and likely higher; color was deep yellow but not orangey. When we did the DPD test the pool water would not turn pink. We were using fresh powder and are very familiar with how to do this test . We have had a Taylor TF-100 kit for at least 10 years, This is the first time this has ever happened. Based on my readings I suspected that the problem was too much chlorine. We did add almost 3 scoops of powder and have never had to add extra powder. I was hoping for better results tomorrow morning after the chlorine has a chance to work on the organic matter in the water overnight as we just opened it today.

 

[mgtfp]

The "yellow" test (OTO) very reliably tests total chlorine (TC = FC + CC). It might just show CC in your case

The FAS/DPD powder shouldn't get bleached until very, very high chlorine levels.

Assuming that your reagents are not out of date, it looks to me like you have no FC (FAS/DPD staying clear), but you have CC (OTO showing something). I can smell Ammonia there...

 

[mgtfp]

Have you done the CC test with FAS/DPD? After not going pink, skip step 3 in the testing instructions and go straight to step 4 (adding R-0003). I'd expect your sample to turn pink then. Titration with R-0871 should then confirm your OTO result as pure CC.

Water Testing Instructions - Further Reading

www.troublefreepool.com

 

[jmb]

Thank you mgtfp for your input! This morning I repeated both the basic chlorine test with K-1000 test kit using R-0600. I was able to also successfully complete a FAS/DPD test. I also repeated the CYA test. The results are promising but a bit confusing.
The basic chlorine test remains a deeper yellow registering at 5. (hard to tell but it seems a little less deep yellow than last night's test)
I proceeded to the FAS/DPD test. The solution turned pink as it should using one scoop of DPD powder; The results were 3.5 FC and 0 combined chlorine. What has me confused is I would have thought I should get at least a total of 5 total chlorine using the FAS/DPD test.
All my reagents are fresh this year.
I know it is early to test my CYA but since I suspected I had some CYA in the pool water I repeated the test. I was still unable to achieve 20 but the water was definitely more cloudy today when placed in the CYA calibrator tube than it was yesterday. Yesterday the water remained completely clear with zero effect on the black dot; today you could see some cloudiness, but I could still see the dot clearly at 20.
Soon I will try raising the FC by 10 ppm as you suggested in your earlier reply regarding testing for ammonia. If I understand correctly, If the free chlorine holds after 30 minutes then I can return the socks with dry stabilizer (which i removed last night and placed in buckets of water ) to the pool water to continue to bring up my stabilizer level.
Thank you again for your input. It was great to learn about several of the advanced testing procedures that you pointed out. Do you have any explanation for the somewhat inconsistent results between the chlorine test using the K-1000 testing kit compared to the results using the FAS/DPD. Are the results small enough to be considered "within a margin of error" or should they be more consistent? Once again my reagents are all fresh this year and I am familiar and comfortable with doing both tests. It is nevertheless a continual learning process as each year I learn more and more as I encounter different issues.

 

[proavia]

The OTO test is more like "is there chlorine in there?" type of test.
The FAS-DPD test is much, much more accurate - and is the definitive test for FC.


The reason the K-1000 kit is included is for the pH test. That provides an accurate pH result at an affordable price point.

As an aside, I use only 4 drops (instead of 5 drops) for both tests in the K-1000 kit.
For FC, 4 drops reads a bit closer to the FAS-DPD test - FOR ME and my eyes.
For pH, 4 drops makes it easier - FOR ME - to compare the results to the colors on the tester.

 

[jmb]

Thank you proavia. I have read these tips elsewhere. Thank you for reminding me of them.

 

[IceShadow]

Did you do the second part of the FAS-DPD test that tests for CCs? EDIT: I see now you did.

I would do the ammonia test again - add 10ppm of FC via liquid chlorine. Mix for 30 minutes with pump going. Test for FC. See if it holds a value.

If it still doesn't, you have two options - you can repeat this until FC holds, or you can first drain and replace some of the water to dilute the ammonia. 1ppm of ammonia takes 10ppm of FC to remove, so depending on how much ammonia you have in the pool, it could take a LOT of FC. If water replacement is an option financially and practically, then you might invest in a low-cost ammonia test like one you can get from a fish store for fish tanks to see if you can estimate the ppm of ammonia in your pool. Then you can estimate how much FC it'll take to get rid of it.

 

[mgtfp]

I just had a look through your PoolMath logs. It looks like the only chlorine you have added so far was 20 litres of 10.8% a day ago. That should have raised your chlorine to 18ppm. If you are now testing 3.5ppm FC then that's a good sign, that shouldn't be there with ammonia after a day.

Maybe it really was just DPD bleaching. I thought that 3 scoops should have been enough, but maybe not. The 4th or 5th scoop might have turned it pink.

I'd still recommend to do the ammonia test, but make sure to get the numbers right. Test FC before adding more chlorine. Then add liquid chlorine to raise FC to 10ppm (if you for example still have 2ppm then only increase by 8ppm). Let it mix for 30min. Then test FC, if you lost more then 80% (i.e. you are below 2ppm), then you have likely ammonia.

Based on the 3.5ppm you have tested, I don't think you have ammonia, but I'd rather be sure on that one. If the test confirms that, then book that test as your opening-SLAM.

 

[jmb]

Before I received your reply I proceeded on the basis that I did not have ammonia based on on the good FAS/DPD results which showed FC levels were holding, no indication of combined chlorine and improving CYA level; also the water clarity is steadily improving. It seems to be progressing as in previous years. The 2 things that threw me off this year was the DPD powder not turning the pool water pink on my first test and having a low CYA. The low CYA is not unexpected as last summer I kept my CYA on the lower range of 30 and we have to drain the pool to close it for the summer. In previous years the CYA was always closer to 40 to 50 and we always had some CYA when we opened. Earlier today I added 3 liters liquid chlorine at 10.8% to keep chlorine at SLAM Levels. I have returned the socks with dry stabilizer back into the pool to bring CYA to ideal level. I will do FAS/DPD tests and keep a close watch on the FC and CC levels. As soon as SLAM is completed I will adjust pH and alkalinity levels as needed. Now if our weather warms up the pool will be ready soon for a swim. This summer I will keep CYA closer to 40 as I am hoping this will help stabilize my liquid chlorine use throughout the summer. I am glad I learned about the ammonia issue as it sounds like I have the perfect conditions for developing that issue and will keep this in mind in future years. Thanks again for your input.

 

[mgtfp]

I think you are on a good way. As I said, I don't think you have ammonia based on the 3.5ppm. If your FC is now showing and holding, you should be good.

And to finally get back to your initial question in more detail:

I would appreciate your thoughts re removing one of the socks and re how much liquid chlorine to add when CYA is less than 20;

If CYA doesn't show in the test (whether it's just below 20 or actually zero is not that easy to tell), and there are indications for ammonia (which was the case for you with the test not turning pink), then we first want to rule out ammonia by adding 10ppm worth of liquid chlorine, before adding any CYA and potentially making it worse by feeding the beast.

Once ammonia is ruled out, and a normal SLAM is required, we would recommend to add some CYA to get it to 30ppm. If not sure if CYA is actually zero, or just below 20, it usually makes sense to add in smaller steps. You don't want to overshoot, but you also don't wan't to SLAM with no CYA. With no CYA, the SLAM level would be 0.64ppm (as you can see in chem geek's FC/CYA table that is linked in the text below the standard table, and is the base for the current chart). That is of course impossible to maintain while UV and algae are munching up the chlorine. Just SLAMMing at something like FC 10ppm without CYA would be an unnecessary strain on pool equipment and you would simply lose too much to UV. Much better to target in this case a CYA level at the lower end of the spectrum to get a well-defined and manageable SLAM-FC.