High TA with No Chlorine measurement

[zingerhill]

Hi All,

I've been using the TFP method for two years now and it's been great. But I am really struggling this year.

I woke up this morning to test the chlorine levels. I usually use AquaChek test strips for daily tests and it was showing zero chlorine. That was not too unusual so I added a gallon of bleach. Usually when I do this and I test right after I add the bleach I get a reading of 10. This time I got a reading of 0.

I figured I would just add more bleach later. So in the evening I added two gallons of bleach and still got a 0 reading. My water has been cloudy, but I would think that I would still show some level of chlorine. I waited an hour and then re-tested and got another zero on chlorine. Then I used the TF 100 kit and this is what I am seeing:

FC: 3 (still seems low given what I had added)
Ph: 6.3
TA: above 200

Is it possible that the high alkalinity is skewing my chlorine tests? I've never had an alkalinity issue. Even if the pool is full of algae like in an opening, the FC still registers as high after an hour when you dump in a lot of bleach. So the whole thing seems quite strange.

Would appreciate any suggestions. I know the test strips are not as accurate as the other tests, but I've found they tend to be in the ballpark on for daily chlorine readings.

Thanks,
David


---
13,000 gallon in-ground pool. Pebble / Concrete
Zodiac Solar Pool Cover, Hayward S-240 Filter, 1.65 HP 110v Variable Speed Pump, Aquacal SQ120R Heat Pump; Using bleach to chlorinate

 

[mknauss]

Test your CC. Also, did this water have CYA in it at closing and what is the CYA reading now.

 

[jblizzle]

I was going to ask exactly the same as Marty.

The TA is not your problem.

Also, stop using the test strips just user the OTO chlorine test daily if you don't want to run the FAS-DPD.

 

[zingerhill]

I'll do the full tests tomorrow. I think my last CYA test was 30.

 

[zingerhill]

So I did the tests this morning and this is what I am seeing:

FC: 0.5
CC: 0.5
Alk: 120
CYA: 0
PH: 6.8

I did Alkaline test twice since it was much different than yesterday. I must have done something wrong yesterday. This is still high but not as high as I thought.

I did the CYA test twice as well since I didn't think this should be zero. I have always had problems with this test, so it's possible that I am not doing it right. I'm surprised it would be this low. I have the powdered stabilizer.

I've attached a photo of the pool where you can see some foaming on the top. I read that this could be a sign of ammonia in the pool and that could also lead to a depletion of CYA and the chlorine. Does that sound plausible to you? The only thing that doesn't fit this explanation is the relatively low CC. I ordered a lot of bleach from Home Depot this morning-- I'm assuming the answer here is going to be SLAM. I also drained a bit of the pool this morning and put in some fresh water.

 

[mknauss]

The water looks fairly clear (though the picture may be deceiving) but I suggest you do a quick test before adding any CYA.
Add enough liquid chlorine to get to 10 ppm FC. Circulate pool at high speed for 15 minutes. Test your FC and CC. Post the results here.

 

[zingerhill]

The pool water actually looks very good now. The foam disappeared since I took that photo at about 8am. I added a gallon of bleach (all I had left) at 11:30 and 15 minutes later the chlorine level was at about 10, which is about where it should be. I can’t check for another hour but it sounds reasonable. Maybe I killed whatever was there. Kids are dying to swim this afternoon. I’m thinking its not perfect but maybe safe enough. Yesterday there was a pool smell and today nothing.

 

[mknauss]

OK -- as long as your FC held after 15 minutes you are good to go to SLAM Process.

You can safely swim in a pool as long as the FC is above the minimum and at or below SLAM level based on your CYA. You must also be able to see the bottom of the pool in the deep end of the pool.