Chlorine usage high. Again

A_kraker99

Well-known member
Jul 18, 2015
103
Zeeland MI
Okay... I have posted about this before but now I am calculating my chlorine usage at about 4.1 PPM per day. I go through just over 4 gallons of 12.5% per week! This just seems really high to me. I passed the overnight loss test and CYA is at 50 so what’s the deal?
I see people at the pool store buying 1 case at a time. I go there and load up 6 cases that only lasts about a month.
 

Newdude

Well-known member
Jun 16, 2019
4,566
NY
Dropping the CYA by 10 to 40 will lower your additions 19 oz a day, which would add up considerably. You are pretty far north and probably don't need the higher CYA.
 

JimMarshall

Gold Supporter
TFP Guide
Jun 5, 2017
1,003
Oil City PA
Hey I recognize you! Lol

additional questions, how long has it been since you passed your OCLT? And did you pass with flying colors or just barely pass? Have you checked all the places organics could be hiding? Drain covers, skimmer necks, light niches, etc?

mans have you checked and double checked your CYA test? How are you performing the test? It’s fairly common to test this level as higher than it actually is.
 

Newdude

Well-known member
Jun 16, 2019
4,566
NY
How would that lower my additions? Doesn’t higher CYA protect it from being used by the sun?
You would drain 20% and refill. CYA is not naturally in any fill or rain water. You are correct that its needed to protect the FC from the sun, but 50 is a tad high for a liquid chlorine pool. Warm climates with high demand may need to go there, but you are much different than San Diego. In your case a 50 CYA needs 77 oz of 12% to gain 4 PPM, but only 58 oz at 40 CYA.
 

JimMarshall

Gold Supporter
TFP Guide
Jun 5, 2017
1,003
Oil City PA
You would drain 20% and refill. CYA is not naturally in any fill or rain water. You are correct that its needed to protect the FC from the sun, but 50 is a tad high for a liquid chlorine pool. Warm climates with high demand may need to go there, but you are much different than San Diego. In your case a 50 CYA needs 77 oz of 12% to gain 4 PPM, but only 58 oz at 40 CYA.
You’ll need the same number of ounces to add 4ppm whether the CYA is 10 or 100. I think what you’re trying to say is that the target number is lower so you won’t have to add as much to get to the target..... but that won’t help the chlorine need at all if his pool still needs 4.1 PPM per day
 

PoolNewb2020

Well-known member
May 7, 2020
302
Lathrop, CA
Not according to pool math. It makes a difference. :cheers:
I don't know. My pool math apps says I need 36oz to go from 6 to 8ppm regardless of CYA level I enter.
Also, when you go to the Effects of Adding section in the app, for FC there is no CYA level required to be filled out in order to calculate FC raise.
 

A_kraker99

Well-known member
Jul 18, 2015
103
Zeeland MI
Hey I recognize you! Lol

additional questions, how long has it been since you passed your OCLT? And did you pass with flying colors or just barely pass? Have you checked all the places organics could be hiding? Drain covers, skimmer necks, light niches, etc?

mans have you checked and double checked your CYA test? How are you performing the test? It’s fairly common to test this level as higher than it actually is.
it’s been about a month since the last OCLT. I think I lost around .8 PPM overnight.
I really don’t have a lot of spots for organics to hide. Just the 2 main drain covers maybe? Could algae under those really use up that much chlorine in 1 day though? I can check them. Not sure if the covers just pop off or not.
I use the procedure on this site to test CYA. I have always been Leary of this test. I am pretty certain I am around 50 though.
 

Newdude

Well-known member
Jun 16, 2019
4,566
NY
I don't know. My pool math apps says I need 36oz to go from 6 to 8ppm regardless of CYA level I enter
If it is set to SWG in settings the CYA doesn’t change the ounces of bleach needed. When I configure my user settings to be like OP’s, it does change the amounts needed based on CYA. Probably because If you have a SWG (or the app thinks you do) the liquid bleach is a supplement and not sole full dose. Maybe it’s a glitch. I dunno. @Leebo, @mknauss what do you guys think ?
 

CrystalRiver

Well-known member
Jun 19, 2020
296
Massachusetts
No matter how I change my settings, it always says the same amount is needed for the same rise in FC.

CYA does not change the chlorine levels. High or low CYA, adding a certain amount of chlorine will always produce the same rise in FC levels. The only thing CYA changes is how quickly that FC gets burned off by the sun, and effectiveness (hence FC/CYA chart).
 
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Chasarms

Silver Supporter
May 8, 2020
347
Dardenne Prairie, MO
4 ppm per day is on the high side of normal. Many people on this forum report such losses. I have as much confidence as anyone can possibly have based the wisdom of this forum and my test results that my pool is quite healthy, yet I lose about 4 ppm of FC. My pool is fully exposed to the sun all day and naturally heats to the low 90s at times.

Higher CYA does not increase chlorine demand. It does adjust the target number upward, but that is a one-time addition. It actually reduces chlorine demand. For example, if you are at 30 CYA with a target of 3-6 FC, and lose three ppm per day, in a week you will have added 21 ppm. If you jump to 50 CYA and a target of 6-8, it's a one-time addition of 3 ppm, but if the daily UV loss drops to 2.5, you're 0.5 ppm ahead after only seven days. Make sense?

In my very limited experience, there are diminishing returns on chlorine protection and CYA. The difference of jumping from 30 to 40 in my pool was pretty noticeable, probably close to 1 ppm per day. The effects of jumping from 40 to 50 were far less obvious. As usual, it is a trial and error process.
 

Psycho1122

Silver Supporter
Sep 29, 2018
92
Mesa, AZ
I found the same result with my conditions. With pool on north side of house and shade sails, I loose 3 ppm per day (June - Aug.) at 40 ppm CYA. 30 CYA is definately too low and the difference between 40 and 50 is negligible.
 
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A_kraker99

Well-known member
Jul 18, 2015
103
Zeeland MI
Thanks guys. My pool does get a lot of sun and this time of year I don't have a solar cover on it (if that blocks UV). Should I be concerned with the OCLT loss of .8 the last time I did it?
I also wonder if my darker liner has anything to do with burning off chlorine quicker. Higher temps near the liner causing increase chlorine usage maybe? Just a thought