Chlorine Usage

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atxjmy512

Well-known member
Mar 19, 2022
215
Austin, Texas
Pool Size
15000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi all -

As we get deeper into summer here in Texas, I'm noticing my chlorine usage starting to increase. I maintain 6 ppm for my CYA level, and up until about two weeks ago i was losing ~ 2ppm per day. Now we're pushing loss of 4 - 5 ppm per day. My water is clear, I'm passing OCLT, and my measured CC is 0.5 or less (usually 0) - so i don't think I am dealing with a nascent algae bloom. This is my first season with a pool thought- so I'm not sure whether something is going on that I'm not seeing in my testing (Taylor K2006C) or if this is just normal usage given persistent 100+ degree days and persistent direct sun with no cloud cover / no rain.
 
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atxjmy512 said:
Hi all -

As we get deeper into summer here in Texas, I'm noticing my chlorine usage starting to increase. I maintain 6 ppm for my CYA level, and up until about two weeks ago i was losing ~ 2ppm per day.
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Well done staying on top of your testing and tracking daily FC loss. I assume your CYA ppm is a typo. Looking at your test log it seems you are dropping out of the FCppm range for your CYAppm. FC/CYA Levels especially lately. We are at peak season now so rise to the occasion. How many bodies are using your pool and how often? Push your FC up to the top end of your range daily now expecting a higher daily loss so that your minimum FC does not fall below proper sanitation levels. You are playing catch up with your FC level and will not keep much longer if this continues.
 
Glad I'm not the only one.

My CYA is 90 and I'm still losing 3 ppm per day. Water is clear; CCs is consistently zero; passed OCLT each of the last two weeks.

I read in John Brace's book that old plaster can become a chlorine draw, and our plaster definitely old. But I don't understand why that would only contribute during the day. One possibility is my daily tests are 24 hrs apart, whereas my OCLT spans 7 or 8 hours.
 
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RickRude said:
old plaster can become a chlorine draw,
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Sorry -- but that makes no sense.

If you are having more cloudless days in the middle of summer than normal, the FC loss will be greater. Here in the land of cloudless days, FC loss stay in the 4+ppm range for about 3 months.
 
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Oly said:
Well done staying on top of your testing and tracking daily FC loss. I assume your CYA ppm is a typo. Looking at your test log it seems you are dropping out of the FCppm range for your CYAppm. FC/CYA Levels especially lately. We are at peak season now so rise to the occasion. How many bodies are using your pool and how often? Push your FC up to the top end of your range daily now expecting a higher daily loss so that your minimum FC does not fall below proper sanitation levels. You are playing catch up with your FC level and will not keep much longer if this continues.
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Thanks!

Generally - in terms of bodies just myself, my wife and our son, occasionally some others once every other week or so but usuage does tend to be daily or every other day albeit for 30 minutes to an hour. Just to make sure I'm understand correctly, you are suggesting I target the 8 ppm upper limit of the pool math recommended range (vs my current 6 ppm target) to keep it from dropping below 4 ppm floor for sanitation levels?

Re CYA Typo - what do you mean? I'm not great at CYA testing - but its somewhere in the 50 - 60 range. The pool math app is spitting back 6 ppm as the target, so that's what I've been shooting for.
 
RickRude said:
Glad I'm not the only one.

My CYA is 90 and I'm still losing 3 ppm per day. Water is clear; CCs is consistently zero; passed OCLT each of the last two weeks.

I read in John Brace's book that old plaster can become a chlorine draw, and our plaster definitely old. But I don't understand why that would only contribute during the day. One possibility is my daily tests are 24 hrs apart, whereas my OCLT spans 7 or 8 hours.
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For what it's worth - my plaster is brand new.
 
Your ozonator isn't helping your chlorine usage.
Shoot for the top end of the FC target range on the FC/CYA Levels. If a high bqther load is anticipated, consider kncreasing the FC a few ppm above the upper target before the swim event. Never let the FC get below the minimum shown on the FC/CYA Levels.
 
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proavia said:
Your ozonator isn't helping your chlorine usage.
Shoot for the top end of the FC target range on the FC/CYA Levels. If a high bqther load is anticipated, consider kncreasing the FC a few ppm above the upper target before the swim event. Never let the FC get below the minimum shown on the FC/CYA Levels.
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Yep... I'm going to start shooting for 8 ppm. Thanks goodness i have a healthy supply of LC.
 
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atxjmy512 said:
Re CYA Typo - what do you mean? I'm not great at CYA testing - but its somewhere in the 50 - 60 range. The pool math app is spitting back 6 ppm as the target, so that's what I've been shooting for.
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In your original post, you said "I maintain 6 ppm for my CYA level". I interpreted that to mean your CYA level was 6 ppm, which couldn't possibly be correct. Hence it must have been a typo. But in actuality, I think we're misinterpreting your language. What you meant was you maintain 6 ppm FC in accordance with your current CYA level.
 
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atxjmy512 said:
I maintain 6 ppm for my CYA level
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I too read this as a typo but I now realize you were referring to FC.
Your daily FC loss is the same unless you get above your target range for your CYAppm so you save nothing and only increase your risk by walking the minimum tightrope. Having a safety net is wise, especially at peak season. Track your daily FC loss after a few days of keeping FC well within the range all 24 hours of each day. I suspect you may see a slight easing of your high FC loss, keep us posted.
 

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RickRude said:
Glad I'm not the only one.

My CYA is 90 and I'm still losing 3 ppm per day. Water is clear; CCs is consistently zero; passed OCLT each of the last two weeks.

I read in John Brace's book that old plaster can become a chlorine draw, and our plaster definitely old. But I don't understand why that would only contribute during the day. One possibility is my daily tests are 24 hrs apart, whereas my OCLT spans 7 or 8 hours.
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The only way this makes any sense is if black algae is living under a flaking and pitted plaster surface. I have seen this issue and without direct access to the B algae it is not easily corrected.
 
RickRude said:
In your original post, you said "I maintain 6 ppm for my CYA level". I interpreted that to mean your CYA level was 6 ppm, which couldn't possibly be correct. Hence it must have been a typo. But in actuality, I think we're misinterpreting your language. What you meant was you maintain 6 ppm FC in accordance with your current CYA level.
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Ahhh... Yeah, I see the confusion. Yes, you're second interpretation is correct. What I meant was for my CYA level of 50 ppm, I target FC of 6 ppm based on the charts. That's on the lower end of the recommended range for that CYA level (50 ppm) and I'll be increasing FC target to 8ppm based on your and others recommendations to avoid dropping below 4ppm.
 
Oly said:
I too read this as a typo but I now realize you were referring to FC.
Your daily FC loss is the same unless you get above your target range for your CYAppm so you save nothing and only increase your risk by walking the minimum tightrope. Having a safety net is wise, especially at peak season. Track your daily FC loss after a few days of keeping FC well within the range all 24 hours of each day. I suspect you may see a slight easing of your high FC loss, keep us posted.
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Yeah i see the confusion point... Typing fast with clarity is not my strong suit... :ROFLMAO: My cya level is 50 ppm (or thereabouts) and I'm targeting FC of 6 based on the low end of TFP recommended range. I'll increase that to 8 ppm. What you are saying makes sense, and resolves a confusion point i had about how i would prevent dropping below 4ppm every day...
 
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Quick update. Took the FC up to 8 ppm yesterday. My testing this morning showed the same general loss ~ 3 - 4 ppm BUT I kept FC above min sanitation levels.

One thing I do wonder about - will 8ppm cause any irritation or discomfort issues for swimmers or any challenges for pool equipment? For instance - my Dolphin robot manual seems to imply they would prefer the robot operate in conditions below 4 ppm. Thoughts?
 
atxjmy512 said:
Quick update. Took the FC up to 8 ppm yesterday. My testing this morning showed the same general loss ~ 3 - 4 ppm BUT I kept FC above min sanitation levels.

One thing I do wonder about - will 8ppm cause any irritation or discomfort issues for swimmers or any challenges for pool equipment? For instance - my Dolphin robot manual seems to imply they would prefer the robot operate in conditions below 4 ppm. Thoughts?
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Have you performed an Overnight Chlorine Loss Test to rule out any possible nascent algae issue?

8ppm FC given your CYA level will not cause any irritation or discomfort to swimmers or any issues for your pool equipment. Most equipment FC max limits are based on having no CYA in the pool water.
 
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proavia said:
Have you performed an Overnight Chlorine Loss Test to rule out any possible nascent algae issue?

8ppm FC given your CYA level will not cause any irritation or discomfort to swimmers or any issues for your pool equipment. Most equipment FC max limits are based on having no CYA in the pool water.
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Yes, I'm passing OCLT. I'm passing all 3 criteria for ending SLAM as well - water is crystal clear, no overnight chlorine loss, and CC is below 0.5. My water temp is pretty warm (90+ by late afternoon), and my pool gets direct sun nearly all day. I feel silly complaining about heat to an Arizonan, but our temps in Austin have been above 100 every day since late May. I'm guessing that's what's driving my daily FC loss.

I didn't know that about CYA and FC level re equipment. That's good to know. Thanks!
 
Given the high heat you have been experiencing, 3-4 pmm FC loss per day is well within what we'd expect.

Remember, most manufacturers, PS, PB and others "in the industry" don't understand or acknowledge the FC/CYA relationship.

At CYA 50 and FC 8, the chlorine is less harsh than CYA 0 and FC 1-2.
It is safe to swim when FC is anywhere between minimum and SLAM level, based on the FC/CYA Levels. And you have to clearly see the bottom of the pool in the deepest section.
 
proavia said:
Given the high heat you have been experiencing, 3-4 pmm FC loss per day is well within what we'd expect.

Remember, most manufacturers, PS, PB and others "in the industry" don't understand or acknowledge the FC/CYA relationship.

At CYA 50 and FC 8, the chlorine is less harsh than CYA 0 and FC 1-2.
It is safe to swim when FC is anywhere between minimum and SLAM level, based on the FC/CYA Levels. And you have to clearly see the bottom of the pool in the deepest section.
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Thanks. The water is so clear in the deep end, i can read the label on the main pool drain.
 
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My CYA is at 60. I typically dose in the evening to get FC up to 11. When I check FC the next evening, it’s usually around six or seven. A couple points above my minimum. I can tell you that even at 11 FC At a CYA of 60, there is zero discomfort to the eyes and my pool does not smell like bleach. Chlorine is our friend.

I’m losing upwards of five ppm of chlorine each day. Pretty much zero rain in the past month or so. Zero rain means our average cloud cover is certainly down, which means our chlorine usage is certainly up.

One thing I would definitely recommend, is check your CYA often. I was under the impression that once it is in there it never leaves aside from splash out and overflow due to rain. However, there are articles in this forum about CYA degradation particularly as pool temperature approaches 90° or higher. I thought my CYA was 60 at one point, I had not measured it for six or seven weeks, and discovered it was actually 30! Measure your CYA :)
 
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If you are losing a lot at 50ppm of CYA then it might be worth pushing the CYA to 60. Your FC targets will be higher but your FC losses should be lessened too. :)
 

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