Why is CYA still low?

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J

jgarden

0
Jun 29, 2014
127
Los Angeles, CA
Pool is a new build, about a month old. I'm trying to get my CYA levels correct. I have put in about 11 lbs of granule CYA and my readings are at 30. I'm pretty sure I am doing the test correctly. I have watched videos and read numerous threads covering the topic. My test kit is about a month old. I last added CYA about a week ago and tested this morning. By most accounts I have added enough for my pool size.

Going to switch over to salt and want CYA at 70.
 
TF100 test kit.

The best way to describe how I am doing the test is that I am following the directions from TFT or if you watch their video that is how I do the test.

Pool was pebbled on June 3. I don't recall the exact dates, but, about a 5 days later I put in 8 lbs of CYA. Unfortunately, I didn't log my CYA readings.

I have the following readings and guesstimates (based on readings) on when I added CYA:

6/24/15 was 20 CYA.

6/27/15 was 10 CYA (I think I added a pound)

6/29/15 was 30 CYA

6/30/15 was 30 CYA

7/1/15 was 20 CYA (I think I added another 2 lbs)

7/2/15 was 20 CYA

7/3/15 was 45 CYA

7/5/15 was 30 CYA

7/14/15 was 30 CYA


Sometime around 6/27, my chlorine level dropped to 0 for a few days (I think bc the CYA was so low, and it was 103 degrees outside and the pool is direct sun, I didn't realize how fast he chlorine would "burn" off) as a result algae took off fast. I slammed the pool and it was sparkling by July 3. Since then it has been sparkling. Not sure if that has something to do with the CYA level dropping. I did read somewhere that the 0 chlorine days will cause CYA to drop.


Thanks for your help.
 
I am sorry I just now saw this. For some reason I am not getting all of my notifications!

I really think you hit the nail on the head! Your low FC caused two big things-algae and lost CYA.

I am glad your water is like a jewel again!

Now you know what to do..........keep your FC up and have fun swimming in your pool!

Kim
 
Mine drops too. I know it isn't supposed to but it does and I do the test correctly.

I should have a CYA of over 100 if it 'stuck' this season. I am at 20 with a SWG and can't afford to buy anymore right now.

I too would love to know what is going on!
 
This begs the question. If letting FC get to 0 will reduce CYA, why would someone drain a pool to reduce CYA? Seems to me the much easier solution would be let pool get to zero FC, which would in turn lower CYA and cause algae. Then you slam pool, get your CYA to normal level and you're back in business. No pool drain needed.

The advice here seems to always be the "ONLY way to lower CYA is to dilute water".

What am I missing?
 
It's not just because the FC drops to 0 that you lose CYA. Usually CYA doesn't go away unless a bacteria is present in the water that breaks down CYA and leaves ammonia as a by product. The bacteria is present because the FC is too low to kill it and it multiplies. It doesn't happen all the time or in every pool. If lowering CYA were as simple as letting FC drop then that is what we would be advising instead of draining, but it just doesn't work that way.

How long has it been since you added FC and what is your current FC level?
 
I was able to get the water back into shape in about 3 days with minimal cost and head ache. Followed slam directions. Used about 12 - 15 gallons of chlorine.

Seems vastly easier than a pool drain? So, do you think my pool wasn't quite at that state which caused the CYA to drop?
 

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zea3 said:
It's not just because the FC drops to 0 that you lose CYA. Usually CYA doesn't go away unless a bacteria is present in the water that breaks down CYA and leaves ammonia as a by product. The bacteria is present because the FC is too low to kill it and it multiplies. It doesn't happen all the time or in every pool. If lowering CYA were as simple as letting FC drop then that is what we would be advising instead of draining, but it just doesn't work that way.

How long has it been since you added FC and what is your current FC level?
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What do you mean by add FC? Are you asking how long since I added chlorine? If so, I add chlorine every couple of days right now. I'm trying to keep the FC around 3-4.

I was/am hesitant to add more CYA, since I believe by weight I've added enough to get my pool to the correct levels.

I think my FC levels are dropping faster than they should due to low CYA. Pool is in direct light most of day and temps over 90.
 
11 lbs should be about 50 ppm CYA in a 24,000 gallon pool. I'd wait a day or two more and test it again. It really isn't something you have to address as an emergency.

The test is difficult on the best days, and given the accuracy of the test, the difference between 30 and 45 isn't a lot. Did you have to waste a lot of water during the slam? If so that may be where part of your CYA went.
 
Bama Rambler said:
11 lbs should be about 50 ppm CYA in a 24,000 gallon pool. I'd wait a day or two more and test it again. It really isn't something you have to address as an emergency.

The test is difficult on the best days, and given the accuracy of the test, the difference between 30 and 45 isn't a lot. Did you have to waste a lot of water during the slam? If so that may be where part of your CYA went.
Click to expand...
I didn't waste any significant amount of water during slam.

Maybe a silly question. 90 % of the CYA was added to the skimmer. Is there any way that stuff is sitting in the filter? The other 10% I broadcast directly into pool.
 
Was it loose in the skimmer or was it contained in a sock? By now it would have time to dissolve either way, so unless you washed the cartridge a day or so after adding CYA to the skimmer it should be showing up on the test.
 
You added to the skimmer as it just poured it in or put it in a sock and let it dissolve that way? If you just poured it in then it might be just sitting there. I would open your filter and see what you can see.

When adding CYA it is best to put it in a sock or two depending on how much you need. You had it in front of the return and let it dissolve that way. That way you are sure it is in the water.

Kim
 
Poured into skimmer. I read about the sock method, but there were also recommendations for direct yo skimmer, including the mfr, so I opted for that. Pump runs 8 hrs a day on a low speed plus a high speed during the slam. I'm gonna assume it's all dissolved by now. But maybe I'll open the filters to be sure.

So basically, if I understand correctly. When my pool got to 0 FC, we have to also assume the starts aligned and that particular bacteria was also created which breaks down the CYA?

Otherwise my CYA readings should be higher?
 
I wouldn't be so quick to attribute it to CYA eating bacteria. It may just be a case of your pool being larger than you think or the CYA being less concentrated than you think. Throw either/both of those in with some testing inaccuracies and you have the numbers you see.
 
I am actually having the same issue. My CYA levels at the end of last summer going into the winter was at 60. Yesterday morning at 8am I tested my pool and my FC was 1.5 and CYA at 40. I have not back washed or swam in the pool yet this summer. At 6am this morning my FC was 3.2 and CYA remained at 40. Pump runs 10hrs a day with the SWG set at 80%. I added TRI-Chlor pucks for now to help bring up the CYA and keep the FC consistent during the day.....So, is there such a thing as a bacteria that eats CYA? I thought you only lose CYA by water leaving the pool?
 
Bama Rambler said:
I wouldn't be so quick to attribute it to CYA eating bacteria. It may just be a case of your pool being larger than you think or the CYA being less concentrated than you think. Throw either/both of those in with some testing inaccuracies and you have the numbers you see.
Click to expand...

Pool isn't larger than I think. It was just built in June. I personally filled it. I noted the water meter reading before I turned on the hose and then again when I turned off the hose. Assuming my water meter is accurate (less than a year old) I think I have a pretty good handle on it's volume. Did the same when I filled the jacuzzi.

As for inaccuracies in my testing that is definitely a possibility. I ordered the CYA standard reagent. It was delivered yesterday. I will test with that to see if I have any clue in how to perform this test.

What do you mean when you say the "CYA being less concentrated than you think?"

thanks
 

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