How fast will it go wrong?

Romoth

Active member
Sep 18, 2020
42
Houston, TX
I'm relatively new to this pool thing (about three months), and maybe this is a stupid question, but I'm trying to understand the margins for error. I'm testing my pool daily with the quick color test and noticed yesterday my FC was about 5 after a full day of swimming (i tested on the back end). Today (without too much sunshine), I was at 1. It was a color test versus last night a titrate test today, so maybe I read it wrong last night. I tested chloramines today and still have zero, so I added enough chlorine to bring me back up to 5. So, my question is, how fast can my pool go from being "ok" to needing to be slammed if I have an issue like today? Is testing chloramines after an error enough to determine if I'm good to go, or will only time tell? I was getting some complaints from wife and kiddo about eyes burning, so I've been trying to keep my chlorine on the lower end and my PH at 7.6. My pool tends to trend up to 7.8, so that's been a little bit of a fight.

I have the same question for PH. I notice mine keeps trending up to about 7.8 and every once in a while I end up at 8 or 8.2 If it hits 8.2 my CSI will be close to .28 or trending up since we've been keeping our water relatively warm to enjoy the mild weather.

Full test results from today are:
FC: 1 (added 72oz of 7.55%)
Chlor: 0
PH 7.9 (adding 7.5 or so oz of 20 baum this afternoon to bring it back to 7.6)
TA: 80
CH: 325
CYA: 35
CSI: .28 (water temp 79)

Bonus question unrelated: I'm gone for the next three days. I'm planning on using pucks in my inline chlorinator. Are there any tips or tricks or things I need to know, or do I just put a few in, put it around low to medium and let it rock. Is it reasonable to bring my FC up to 7 or 8 before I leave? I have a house sitter who would like to use the hot tub while we're gone, so don't want to have the chlorine ridiculously high so I can protect her eyes and skin!

I know there's a lot here, so thanks for any help you're able to provide.
 

ajw22

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TFP Guide
Jul 21, 2013
22,153
Northern NJ
Pool Size
35000
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Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Do a Overnight Chlorine Loss Test to see if you have an algae problem brewing.

Your CYA is 40. If the dot disappears between 40 and 30 we round up and call it 40. You cannot eyeball values between the lines since the scale is logarithm, not linear.

See the FC/CYA Chart. Target FC for CYA 40 is 5-7 with a minimum of 3. You are safe to swim up to SLAM FC level which is 16. So a FC of 8 is perfectly safe for your sitter.

With your FC falling below the minimun of 3 there is a good chance you picked up some algae and bacteria which is causing the complaints of burning eyes.

Keeping the FC low is not a good strategy. In a sanitary pool you will never be able to feel the difference in chlorine level between the minimum and SLAM FC level. Follow the FC/CYA Chart levels.
 
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Romoth

Active member
Sep 18, 2020
42
Houston, TX
A lot to unpack here and a few additional questions:
  • Thanks for the clarification on CYA levels. I'll be sure to always round up instead of thinking "middle of the road"
  • I think I was under the impression that chlorine was causing the eye irritation. Duly noted that's not the case. I'll make sure to keep it on the higher end of the spectrum with 40 CYA so I never fall below minimum.
Now for my remaining questions:
  • I'm going to go bring my chlorine up to 7 in a few minutes. Are we safe to operate the hot tub tonight if I have an algae/bacteria problem blooming? We have a few close friends in from out of town and they're pumped about the hot tub. I can cancel, but ideally I wouldn't have to as the wives have been planning this for a while.
  • If we're ok to hot tub tonight, I figure I'll add chlorine shortly after they leave and test it 30ish minutes later before I go to bed. I can get up and test tomorrow morning and see my overnight loss. My understanding is if I have no overnight loss, I'm good to go. Assuming that's not the case...
  • Is this likely to "explode" prior to me getting back on Friday (I'll test and add chlorine tomorrow before I leave)? Is raising the chlorine before I go and telling the sitter not to swim potentially help manage the potential impacts until I can deal with it, or does that not add any value?
I really appreciate the help. I'm hopeful I'm good with an overnight test, but my gut is that's not the case and I'll get to enjoy my first SLAM. I didn't even make it three months! :(
 

ajw22

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TFP Guide
Jul 21, 2013
22,153
Northern NJ
Pool Size
35000
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Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
  • I'm going to go bring my chlorine up to 7 in a few minutes. Are we safe to operate the hot tub tonight if I have an algae/bacteria problem blooming? We have a few close friends in from out of town and they're pumped about the hot tub. I can cancel, but ideally I wouldn't have to as the wives have been planning this for a while.
If the water looks clear then I would raise your FC to 8-9 for the night qnd enjoy your soak with your friends.

  • If we're ok to hot tub tonight, I figure I'll add chlorine shortly after they leave and test it 30ish minutes later before I go to bed. I can get up and test tomorrow morning and see my overnight loss. My understanding is if I have no overnight loss, I'm good to go. Assuming that's not the case...
Yup, raise your FC up around 7-8 in your pool and do the Overnight Chlorine Loss Test

  • Is this likely to "explode" prior to me getting back on Friday (I'll test and add chlorine tomorrow before I leave)? Is raising the chlorine before I go and telling the sitter not to swim potentially help manage the potential impacts until I can deal with it, or does that not add any value?
See how much your FC loss is on the Overnight Chlorine Loss Test. The amount of chlorine loss is sort of proportional to the extent of algae you have.

I think you want to raise FC up to 12 before you leave. Do you have liquid chlorine and do you trust the sitter to add a measured dose to the pool?

I really appreciate the help. I'm hopeful I'm good with an overnight test, but my gut is that's not the case and I'll get to enjoy my first SLAM. I didn't even make it three months! :(
This is all part of your learning about pool water chemistry.
 

Romoth

Active member
Sep 18, 2020
42
Houston, TX
I can definitely ask the sitter, but I'm not sure how comfortable she'll be with it. I've got an inline chlorinator that I was planning to turn on to about a "medium" while I was gone if she can't. I know that will add CYA also, but that was my plan. As it relates to tonight, I'll plan on having a good soak.

What would my best practice be for the test? Do I add some chlorine as soon as we're all out (enough for a couple PPM) and test it thirty minutes later and record that value? Will us swimming mess up the results?

Thank you again for all the help, I really appreciate it!
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
22,153
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
You are soaking in your spa. It should not change your FC in your pool. Do the Overnight Chlorine Loss Test on your pool. While the directions say to have at least 3ppm of chlorine I would want 5-7 ppm for the test.


To perform the overnight FC loss test:
  1. If you have an SWG, tablet chlorinator, or other chlorine feeder, shut it off completely.
  2. After the sun goes down, and at least 30 minutes after your last chemical addition of the day, test your water for FC using the FAS-DPD test making sure your FC level is at least above 3ppm.
  3. Record that result. Do not put any more chlorine in your pool.
  4. The next morning, as early as practical and definitely before there is any direct sunlight on the pool, perform the FAS-DPD FC test again and record the results.
If your FC level remained the same, or went down by 1.0 or less, the water is clean. There isn’t any living algae or other organic contamination in the pool.

If you lost more than 1.0 ppm of FC, then there is something in the water that needs to be removed and you should SLAM, or continue SLAMing, the pool.
 
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HermanTX

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May 20, 2020
1,168
Katy TX
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If you are only going out of town for 3 days, then bringing your FC up to over 8 - maybe higher as suggested by others will be fine. I use a floater for my pucks (I don't trust that the inline chlorinator really is effective). I add 3-4 pucks. When you get back home you find you have some erosion of your pucks but not completely gone. I add them as I the last thing I do before leaving and I remove them directly upon return It be safe for your sitter to swim as well.
 

Romoth

Active member
Sep 18, 2020
42
Houston, TX
I did the OCLT and only lost .5PPM. I'm using the TF-100 test kit with a speed stir, so I feel pretty confident about the results. The water is beautiful and clear and I learned a lesson about being more conservative in my chlorine. Thanks for the advice! It looks like I got lucky on my water.
 
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