Chlorine Loss?!?!

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
A few weeks ago, I had what I assume was an algae bloom. Water temperature was in the mid 80s from the previous weekend. It was a chilly week and nobody was using the pool. I was working long hours and didn’t check chemicals from Sunday to Thursday. When I removed the cover Thursday evening for the kids, the water was super cloudy and circulation was awful because my de filter was ‘clogged’. My fault...lesson learned there. It was really the first issue I’ve had since becoming a pool owner lart year and finding this site right away.

So...I slammed. Ph was ok and I brought the pool right up to shock and kept it there. I brushed twice a day, vacuumed once per day...the cloudy algae (?) was dissipating quickly and was showing up on the bottom as brown heavy powder (best I can describe it). I was having to change my de about every four hours as it was clogging that quick. But...less than 48 hours later the pool was crystal clear and I was all the wiser.

I maintained shock level until the water was crystal clear, cc was 0, and passed the oclt...at least I think. my oclt was ‘bordeline’ but I was out of reagent because of the slam. I was sure I was good and let it drop to normal levels while I waited for more reagent in the mail.

Since that time, the pool has been using what I think to be a lot more chlorine than last year (going by memory). It had been in the back of my head that just maybe that last oclt wasn’t quite less than 1 ppm loss.

My pool gets pretty heavy use. My wife and two kids are home all summer and we have frequent guests use it. It’s also been very sunny and hot. The pool gets a solid 8 hours of 100% full sun every day and the cover is usually off most of that time.

My water has been absolutely crystal clear this entire time (as it always is)... Never even a hint of cloudiness or anything. I was also noticing my eyes were irritated much more than last year which I attributed to cc because everything else was fine. I was occasionally getting a 0.5 cc reading but not every day.

cya has been around 50 all season.

ph has been hovering on the low end of range 7.2-7.4. I’ve added washing soda a couple times to get it up.

Ta has been 90-100 all year.

Last weekend I did a three hour tsp soak followed by a three hour MA soak of my de filter ‘fingers’ just to make sure I undid any ‘damage’ Done by the algae bloom...I had it in my head that my pressure hadn’t quite been the same. The cleaning of the filter put my mind at ease but didn’t have any effect on the pressure...better safe than sorry I guess. and I’ve still been using ‘more’ chlorine.

My chlorine use was probably averaging one to one and a half gallons per day of 12.5% liquid chlorine in an approximately 20 k gallon pool. I tend to aim for the high end of ‘target’ (maybe even a touch higher) and let it fall through the ‘zone’.

So. I did a couple oclt with a borderline pass/fail in night 1 and screwy results in night 2 (FC went up??? Which I know isn’t possible...and yes-I gave it plenty of time to circulate before doing the night test).

i finally had Enough speculating and decided to just slam the heck out of it again. I figured if I have a tad bit of left over algae it’s not going to take much. Yesterday evening I added five gallons of liquid chlorine which should have brought me up to 30 ppm (I didn’t check after adding it) and brushed every inch of the pool.

five hours later, fc was atound 15! What the heck! I over zealously added another five gallons and checked about an hour later. Now I was at 44! Oops! I left the ladders out to be safe. I have no other items in the water-just a skimmer and return jet. Early This morning on the other end of the oclt, I was at fc 40 with cc 0.

I disassembled and scrubbed the ladders with chlorine solution this morning and dipped them in the pool to ‘rinse’ the higher concentrate solution. I have not reinstalled them yet.

This evening, I’m back down to fc: 15. Cc: 0-0.5. I’m not sure if it even turned pink or not.

Im going to return it to shock level overnight and do another oclt. I hope to find that it passes but why did the pool use 25 ppm today? Nobody swam in it. It was sunny. I did confirm cya of 50 again. I’m worried that I will pass the oclt and cc tests in the morning but will continue to use up chlorine every day!

I feel like I’ve dine everything right and can’t figure this out. Help!

sorry for the long post but I wanted to provide the entire context because I feel I’ve already researched thus to death on this site.

Thanks in Advance fir your time.

- - - Updated - - -

One thing I forgot to mention is I’ve left the cover off for this slam to take it out of the equation like the ladders.
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Not sure I follow. I didn’t backwash much water. It probably takes me less that 25 gallons of water to change my media. I have lost water to evaporation/lack of rain and had to add it a couple times via my city water but I’ve probably exchanged a total of under 1,000 gallons all year. Rain included.

I wondered about the cya myself but have fun the rest several times (including with new reagent) with the same result.
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Fc 32
cc 0.5
(very light pink with cc reagent added after fc test - clear with one drop - 10 ml test sample)
after sundown tonight.

Fingers crossed for morning
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Morning
fc 29
cc 0.5
cc was very light pink before adding the single drop to make it clear so I’m thinking less than 0.5.
Keep slamming, I guess?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,024
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Yes.

What does your water look like?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,024
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Great. Keep at SLAM levels today and do another OCLT tonight. If you have just over a 1 ppm loss in the morning, then I would suggest letting your FC drop to mid teens the next day and then do another OCLT. At times trying to do a OCLT at elevated FC values is problematic as testing error is as much or more than your 1 ppm FC.
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Pool store tested my cya at 8!!! That could expand my problem easily.

do I trust them? Or my tests with the Taylor kit?

im out of cya test reagent at home. Is there another test I can do. Maybe get another pool store opinion?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,024
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
You have the best test kit made. Use it. Believe it. Quit getting pool store tests.
 

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demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Marty,
tganks for reassuring me. I had to get chlorine there so I figured I’d get a check on my cya.

richards reply above. had me thinking about it.

the pool store test had my TA at 0 which frankly scared the heck out of me! And also had me doubting my kit.

Ill keep the faith!
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Jus checked levels at 12:50
fc 20
cc 0

the fact it is using fc so much faster during the day leads me to believe cya might actually be the issue. I took a five gallon bucket of water out of the pool and put it inside in the dark. Didn’t change anything else. I’m going to check the bucket and the pool after work. If the bucket stays the same and the pool drops another 10 ppm or so, isn’t it safe to say I need cya? Not sure why my test would be off but I can’t figure out why it would use so much more during the day. There has been no use of the pool today nor was there yesterday when I had similar results during the day.

am I missing something? It all just doesn’t add up.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,024
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Just follow what I described in Post #8. Not sure what the bucket thing would imply ----
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
My thought was by keeping the bucket inside in the dark, it would eliminate loss due to sunlight. I would be able to compare a bucket text to a pool test at the same time.

If the pool continues to drop but the bucket maintains fc, wouldn't that be a good check on where the fc is going?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,024
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
OK. I would not hang my hat on the results but might be interesting.
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Passed oclt

17.5 fc
0 cc

Exactly the same last night and this morning.

Im willing to bet I lose 5+ ppm between now and 12:00 noon. I really think my cya test was off. Ive been getting the same result all season with the same bottle of refill I ordered at beginning of season-that bottle is gone now...I’m thinking I had a bad bottle or something. I ordered new reagent but it won’t be here until Monday (and Tuesday I leave for vacation! :mad:).

what to do?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,024
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
CYA reagent is the most stable one there is. So the chance of having a 'bad' bottle is pretty slim.

I assume the CYA in your water is a carryover from last year and you have not added any actual product to the water this year? What was your final CYA test from last year?

Until Monday see if your FC will stay in target level using normal (2-4 ppm FC) amounts of chlorine each day.
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Last year I stayed right in the 40-50 range.

This spring, I was at 0 at opening. I added the necessary (I think I remember around 6-7 lbs) granular stabilizer and have been reading 50 all season since. Stupid me put it in the skimmer rather than using the sock method but it did register correctly after a couple days.

thanks for the continued replies. I’ll take your advice and wait til Monday for the new reagent. Maybe it will come early.
 

demilio56

Bronze Supporter
Apr 25, 2017
62
Binghamton
Marty,
Just to clarify...I have been keeping everyone out of the pool, leaving the cover off, leaving the heater off, leaving the PUMP ON, and even took the ladders out the last couple days to eliminate everything possible from the equation.

With that said, is there ANY reason other than CYA that would explain losing chlorine during the day and not over night?
 

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