Need help to get my levels right..

LHK

Silver Supporter
Jun 11, 2020
31
Cincinnati, OH
Hello! I come here often for help, but this is my first time posting.

I am going through what seems to be an insane amount of chlorine - 10+ jumbo tabs each week for a 13,000 gal pool. I put 4 in at a time in the in-line chlorinator and they're gone in 2-3 days. It has been 80-90 deg and sunny nearly all day every day for the past few weeks, so I know that is a factor, but this still seems like too much. CYA is 35 as measured with a Taylor kit. I also use one bag of shock about once weekly (says it treats 13,500 gal), or 3 bags when the combined chlorine gets high. I shock at night and by morning the free chlorine is back to 1 ppm. We swim nearly daily, sometimes have neighbor kids over as well, so the pool does get a lot of use.

This is only my second year with the pool, so I'm still learning. Is this normal when it's hot and sunny out? Do I need to get my CYA closer to 50? Am I missing something?

Thanks!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
32,622
Laughlin, NV
Welcome to the forum!
For a reality check, 10 trichlor tablets a week would add ~30 ppm CYA to your pool. But you are only testing that much CYA. So something does not add up. And that does not include the 'shock', if that is dichlor.
What Taylor Test kit are you using?
I suggest you read ABC's of Pool Water Chemistry.
 

LHK

Silver Supporter
Jun 11, 2020
31
Cincinnati, OH
I'm using the Taylor K-2005 test kit (updated in my signature). I just got this test kit this season, so all the reagents are new.

Values as of this afternoon:
FC 1 (Just lighter than the color match for 1-2)
TC 1.5 (The exact color match for 1-2)
pH 7.0 (This was closer to 7.2 this am)
TA 80
Water is beautifully clear
I've attached the chlorine tabs and shock I've been using

I've actually read the ABC's of Pool Water Chemistry and feel that I have a reasonable grasp on the basics. I'm doing a much better job with maintaining the pool this year compared to last year when I struggled with algae on and off all season. This just seems like a lot of chlorine.

Thanks for your help!
 

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
32,622
Laughlin, NV
Again, you are adding 30+ ppm CYA per week. So your testing is not correct or you are draining and refilling the pool by large quantities.

I suggest discontinuing the tablets and shock and follow TFPC. Use bleach and follow the FC/CYA Chart
 
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LHK

Silver Supporter
Jun 11, 2020
31
Cincinnati, OH
OK, a few questions before I can start:

1. I'm not sure what's wrong with my CYA measurement, but I need to know it to get the proper SLAM chlorine level, so...any suggestions why this would be so far off? I reread the test instructions to make sure I did the test correctly, and I did. It read the same when I tested it at the start of the season. I've been using these chlorine tablets all last year and this, so why isn't the CYA reading higher? We have not drained our pool.

2. The test kit I have has a color for 10-20 ppm of chlorine - if my CYA is actually 35, I need to keep the chlorine at 12 or above, so couldn't I use this kit?

3. I've never used liquid chlorine before. We bought the tablets last year before I found TFP, so we're still using them up. How many gallons does one typically use to SLAM? I recognize this depends on MANY factors, but I'm just trying to get an idea of how much I need to get from the store to start the process.
 

LHK

Silver Supporter
Jun 11, 2020
31
Cincinnati, OH
We've had very little rain.

I still don't understand why I can't use my current Taylor kit for the SLAM process if I can tell when the chlorine is in the 10-20 ppm range and I have done an OCLT with it. Is this not accurate enough? Am I missing something important that my kit can't do? If I do need to buy more testing supplies is the one below ok? (I don't need another full kit.)
 

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
32,622
Laughlin, NV
You can do as you want, it is your pool. We just do not provide guidance to that effect. If your kit can measure 1 ppm drop from 16 to 15 ppm, great.
 

LHK

Silver Supporter
Jun 11, 2020
31
Cincinnati, OH
I see now why the other kit is needed, thank you.

I appreciate your expertise on the subject, although I do feel that the delivery of the information has been unwelcoming and offputting. I'm not saying this out of anger or retaliation, but rather so that you're aware of how it comes across in case that is not what you intended and would like to adjust your approach accordingly. Again, thank you for your help.