CYA Rose Sharply Overnight After Start of Slam. Continue?

AzKraken

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Hello all,

I am just starting to learn about pool chemistry and have lurked and read on the site quite a bit, but excuse my ignorance in advance.

Bought a new house with a pool a few months ago. Pool was sparkling, but not knowing much about pools, I maintained it with pucks (what the previous owner was using). I had no issues, but when on vacation, my pump went belly up and we had a bad season of dust storms and monsoon weather simultaneously. I couldn't get the pump replaced for several weeks due to demand...and I was hit with a pretty serious algae bloom.

Wanting to get serious about understanding what to do, I finally (thankfully) found this site. However, after getting a test kit from the recommended list (Taylor 2006), I found that my CYA levels were off the charts. I tried to accurately measure them, but they were at least over 200. After lurking through previous posts, I realized that drain and refill was really my only option. As its been extremely hot here in PHX, I opted for a simultaneous pump and fill exchange (my poor water bill). After pumping and filling approximately 20k gallons (from an estimated 14500-15000gal pool) I finally got my CYA into manageable territory last night, measuring twice at ~60. I checked this test several times and had my wife also run the test to confirm. I rounded up to 70 in my calculations just to be sure. Then, I followed SLAM protocol. Lowered to the PH to recommended levels and then added liquid chlorine to recommended levels, brushed, and skimmed as much as I could.

Overnight, I was happy to see a noticeable reduction of green tint and an increase in water visibility. I had lost about 40% of my FC, and went to add more when I decided to check my CYA again. This morning, the CYA levels were between 90-100. I have not added anything but liquid chlorine (10% sodium hypochlorite)...and I am confused how my CYA levels could have risen that much overnight. I have read elsewhere that CYA can leech from plaster, but it seems like most posters on this site only attribute CYA rising to tester error. While this is possible, I was continually testing and watching the CYA lower as I drained, so I am relatively confident in my readings.

My question is: should I continue the SLAM protocol and simply factor in for a higher CYA or should I stop, let the FC level drop (city asks for as neutral water as possible when pumping to sewer at high quantities) and begin the water replacement process again? I am worried if I dont understand why the CYA is rising I might get stuck wasting a ton of water.

Sorry if this question has been answered elsewhere, but I couldn't find anything definitive.

All the best and thanks in advance!
 

Texas Splash

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Welcome! :wave: You could do either. You could exchange a little more water if you wish, or just balance the FC to a slightly higher CYA level - using perhaps 80 for now? There really shouldn't be any good reason for the CYA to change, but perhaps the time of day, lighting, or some other variable was the reason? I would give teh CYA one more test this evening and go with that one.
 

AzKraken

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Thanks for the quick reply. I'm sure that lighting or error is the case, but it was hard to swallow confirming a level of 60 several times last evening to a level back up to 100. Given how bad the algae is, I think I will attempt to keep the levels high and clean the pool up a bit before I re-evaluate. I don't want to get the pool beyond recovery.

I will keep SLAM protocol at CYA ~90 and retest CYA this evening before I make a decision to drain again.

Thanks again!
 
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AzKraken

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Update:

I have continued the SLAM process for a day and a half now. Seeing obvious improvements, but still have a long, long way to go. CYA still testing ~80-90. Other than testing error, the only thing I can think of they CYA rose is due to there being concentrated amounts in the pipes/filter/motor that was not running during the drain cycle.

Still losing a considerable amount of FC ... stocked up on liquid chlorine, so I am going to continue with the SLAM and filter process for the next few days at least and see where I am at. I'm hoping that I can lower the CYA at least a bit as I am having to backwash the filter a decent amount. I'm estimating, but flushing twice a day for a week will

Ive attached some progress pictures. Water is still pretty cloudy but the color is certainly shifting blue quite a bit. No more deep greens (it appears more green in the final picture than in person). I'm seeing more clarity on the sides of the pool and can see deeper each day.

I
 

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Mdragger88

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I suspect lighting is the major culprit of testing error. Full sun is best.
Back to the sun, tube waist high, pour , glance, pour etc.
You can pour the mixture back into the squirty bottle, shake & re-do the last part of the test as many times as u need to get an average.
Glad things are coming along
 
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AzKraken

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I am guessing that you are right. Right now the plan is to get major issues under control and then slowly continue to lower my CYA via partial drains and backwashing over time to the point where if I must use a few pucks while I am away, I don't create more problems. Meanwhile, I plan to research and learn how to do a deep cleaning of the sand filter. Right now it appears to be working, but I have no idea how long it has gone without any servicing or attention!
 

Mdragger88

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Here’s the link for that write up 👇
 

Bperry

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If the water isn’t clear yet, that affects the visibility of the black dot lower so that may be causing the CYA to read higher than it really is. If you have algae you’ll be backwashing anyway so even if it is higher, it’ll go down if you don’t add any more CYA.
 

HermanTX

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If the water isn’t clear yet, that affects the visibility of the black dot lower so that may be causing the CYA to read higher than it really is. If you have algae you’ll be backwashing anyway so even if it is higher, it’ll go down if you don’t add any more CYA.
One way to verify if cloudy water is affecting your CYA test is to simply fill the tube with only pool water. If you can see the black dot clearly with a full tube, then your CYA test should be reasonably accurate with the mixed solution.
 

AzKraken

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One way to verify if cloudy water is affecting your CYA test is to simply fill the tube with only pool water. If you can see the black dot clearly with a full tube, then your CYA test should be reasonably accurate with the mixed solution.
Thank you for the advice. I will do this and see. I think, however, that it was likely just original error/wishful thinking bias to start.
 

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AzKraken

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Update:

The pool water is now virtually crystal clear. I can easily see the bottom on the pool. Unfortunately, it seems that I have a massive black algae infestation (virtually the entirety of the bottom of the pool has it). I have wire brushed the heck out of it and tried to keep my FC at the levels Pool Math reccomends for my CYA (FC 12). However, I am wondering if I am fighting a losing battle with such high CYA. I havent seen any improvement in a few days. Is this simply a time situation or should I be looking to do another water exchnage?
 

Bperry

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Update:

The pool water is now virtually crystal clear. I can easily see the bottom on the pool. Unfortunately, it seems that I have a massive black algae infestation (virtually the entirety of the bottom of the pool has it). I have wire brushed the heck out of it and tried to keep my FC at the levels Pool Math reccomends for my CYA (FC 12). However, I am wondering if I am fighting a losing battle with such high CYA. I havent seen any improvement in a few days. Is this simply a time situation or should I be looking to do another water exchnage?
Post your water readings to people can take a look. If you’ve been doing the slam process, you’ll need to keep going to get rid of it. If you haven’t, then you can start slamming. I had some small black algae spots and chlorine and minor scrubbing got rid of them.
 

AzKraken

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Post your water readings to people can take a look. If you’ve been doing the slam process, you’ll need to keep going to get rid of it. If you haven’t, then you can start slamming. I had some small black algae spots and chlorine and minor scrubbing got rid of them.
I should clarify as this is an older thread. I have been SLAMing for 7 days now. Major improvements except for the the bottom of the pool (and a few on the sides). I have virgorously scrubbed with a wire brush for several days in a row. Wondering if I need to either drain to lower CYA or raise my chlorine levels insanely high for a night or two.

Attaching pictures to show the extent of the problem.

FC: 12
CYA: ~90
 

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Bperry

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I should clarify as this is an older thread. I have been SLAMing for 7 days now. Major improvements except for the the bottom of the pool (and a few on the sides). I have virgorously scrubbed with a wire brush for several days in a row. Wondering if I need to either drain to lower CYA or raise my chlorine levels insanely high for a night or two.

Attaching pictures to show the extent of the problem.

FC: 12
CYA: ~90
If your CYA is 90, then your FC for SLAM is much higher than 12. I think you may have mixed up the charts. Click the “SLAM” button on this page to check it. 12 ppm is your normal FC level. SLAM level is 35. You’ll probably want to drain some of that off.

 

mknauss

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That does not look like black algae. I suggest you get some of it and smear it on a paper towel. If it smears blue - green, it is black algae.
 

Bperry

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I was also going to say it doesn’t look like black algae. It could be but it looks like small spots. SLAM level chlorine should take care of that if it is algae.
 

AzKraken

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If your CYA is 90, then your FC for SLAM is much higher than 12. I think you may have mixed up the charts. Click the “SLAM” button on this page to check it. 12 ppm is your normal FC level. SLAM level is 35. You’ll probably want to drain some of that off.

You are 100% right. Using the app and I didnt see there was a slider under the SLAM reccomendation that changed. it. Should be at FC35. Not sure if that is sustainable for any period of time...that is about 40$ a night at local chlorine prices. Might be time to start draining again
 

Tcadwall0

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AzKraken

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That does not look like black algae. I suggest you get some of it and smear it on a paper towel. If it smears blue - green, it is black algae.
interesting. I will try to get some, but most of it is in the deeper sections of the pool. It was not present before this algae bloom, so I am confused as to what it would be since it wont come off with any sort of brushing or vaccuming
 

mknauss

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Honestly looks like a metal stain. Copper would be one. Any use of copper based algaecides or trichlor pucks with copper in them?
 

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