Problem with liquid chlorine and pool calculator

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Chaya

Bronze Supporter
Jul 28, 2019
72
Lakewood, New Jersey
hi all -
i'm pretty new to this website and based on help i received last year i am trying liquid chlorine for the first time.
so far its a total flop!

1) according to PoolMath one gallon of 12.5% chlorine should add 6ppm of chlorine to my 21k gallon pool. but it does not seem to. i have been adding a full gallon a day and it never goes that high. more like 3.5-4.5 ppm

2) there is talk of chlorine/plain bleach being cheaper than 3" tabs i've used in the past. i am finding that it is costing more than 3 times the price!
in past seasons i buy one 50lb bucket for about $100 and it lasts the season. so far this season i have been using 1 gallon of chlorine each day ($5.50 each plus tax). not only is the price prohibitive but i am struggling to keep the chlorine levels high enough. a full gallon is getting used up each day and i'm back to my morning levels (pre-chlorine addition) each evening. when i used tabs in past i put in 4 tabs and chlorine consistently stayed at 8ppm exactly where i need it. i saw some threads where there was discussion of very cheap liquid chlorine prices but could not find any of these prices locally (lakewood, NJ)

these are my numbers:

alkalinity 80
ph 7.4
chlorine 6
fc 6
cya 60

i have a 21,000 gallon vinly liner pool with sand filter

at a cya of 60, my chlorine should be from 7-9. so far, its never there. maybe first thing in the morning after i add chlorine. after that it drops to 6, by night its 4. i am not losing chlorine overnight, my water is gorgeous crystal clear sparkling water. with a morning FC level of 4, i should be able to add a gallon of chlorine and get 10ppm which should last for the day. but its not happening. its not going high enough and its getting used up too fast (i have read that you can expect 2-4ppm to be used up during the day but i seem to be using more...

what am i doing wrong?
 
First thing is to check the date code on your chlorine, especially if you bought it at a big-box hardware store. People have reported finding stuff from last season! Bleach degrades, so it would be half strength or maybe even less, which tallies well with what you're experiencing. There's some good info here

Chlorine Date Code Decoder/Easy Way to Measure Strength.

Hi, I just joined TFP this season and pool is looking great. TFP is an awesome resource. Thanks I thought the information below might be helpful for some of the forum participants. I recently bought 1 jug of 10% Liquid Chlorine that was actually 4.5%. It had a 2013 date code. I now am very...
www.troublefreepool.com www.troublefreepool.com
 
Pool math is spot on for my 14k gallon pool.
Are you measuring your FC about 30 minutes after adding liquid chlorine? If so, what test are you using?

What will throw off Pool Math calcs is incorrect pool volume, incorrect chlorine strength selected in the app or simply old chlorine that lost its potency.
 
Bleach is definitely harder to come by this year in NJ. The Ocean State Job Lot that used to sell it for $3/gal near me is closed, and I haven't seen it at any Lowe's/Home Depots around here. Luckily a pool store near me sells 5 gallon jugs for $20, which isn't too bad.

Also, for reference, my 40k gallon pool has been using about 1/2 gallon per day.
 
Richard320 said:
First thing is to check the date code on your chlorine, especially if you bought it at a big-box hardware store. People have reported finding stuff from last season! Bleach degrades, so it would be half strength or maybe even less, which tallies well with what you're experiencing. There's some good info here

Chlorine Date Code Decoder/Easy Way to Measure Strength.

Hi, I just joined TFP this season and pool is looking great. TFP is an awesome resource. Thanks I thought the information below might be helpful for some of the forum participants. I recently bought 1 jug of 10% Liquid Chlorine that was actually 4.5%. It had a 2013 date code. I now am very...
www.troublefreepool.com www.troublefreepool.com
Click to expand...
the chlorine is "shock it" by alliance trading in covington, la. googled telephone number, can't get through to anyone. called retail pool store and they are assuring me its new but have no information on the manufacturer. The numbers stamped on bottle say "20 143 0817 q1 1672-MA-1"
Chances are the "20 143" is the year and day and that is pretty fresh - just a few weeks old.
 
PoolNewb2020 said:
Pool math is spot on for my 14k gallon pool.
Are you measuring your FC about 30 minutes after adding liquid chlorine? If so, what test are you using?

What will throw off Pool Math calcs is incorrect pool volume, incorrect chlorine strength selected in the app or simply old chlorine that lost its potency.
Click to expand...
i'm testing with taylor test kit 30-60 minutes after addition.
 
TO116 said:
Bleach is definitely harder to come by this year in NJ. The Ocean State Job Lot that used to sell it for $3/gal near me is closed, and I haven't seen it at any Lowe's/Home Depots around here. Luckily a pool store near me sells 5 gallon jugs for $20, which isn't too bad.

Also, for reference, my 40k gallon pool has been using about 1/2 gallon per day.
Click to expand...
so my pool is clearly using WAAAAY too much! it is in FULL sun all day. how much of a difference does that make? is yours also?
 
TO116 said:
Actually no, its in full sun from about 12-7.

Since it doesn't register what pool math says it should, I'm more inclined to believe you're volume is off.
Click to expand...
except i have the paperwork from the manufacturer, foxx pools, and it works for my alkalinity additions and always worked when i brought my water sample to the pool store.

maybe i should try again over the next few days.
 

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Chaya said:
except i have the paperwork from the manufacturer, foxx pools, and it works for my alkalinity additions and always worked when i brought my water sample to the pool store.

maybe i should try again over the next few days.
Click to expand...
It's irrelevant what the paperwork says. If the liquid chlorine is fresh and the app is set up with the correct concentration, then that leaves the volume number as questionable.

Also, your FC levels are the most important aspect of keeping your pool trouble free, alkalinity is not. So I would make sure the app calculates the additions correctly.
I would try increasing the pool volume in the app until the levels suggested match with the actuals.

Also, I just saw you use taylor test kit, but didn't specify which one. Are you using the FAS/DPD to test FC?
 
How soon after additions are you testing the water to verify that it went up as expected?

What tests are you using to get your FC levels?
 
ok all. i tried again with your encouragement that the pool math HAS to work. originally i added once pump went on (about 9am) and it was sunny, so i was losing chlorine as i was adding. I got my pool paperwork and changed volume of pool the the exact 21,480 gallons on the calculator. 121 oz should raise my chlorine from 4.5 to 10ppm. 1 gallon DID raise my chlorine from 4.5 to 10 on June 15th, 16th and 17th. at end of each day it was back to 4.5. yesterday was cold, no sunshine and rainy at times. at end of day it was 5 or 5.5.

So in general i am indeed using 5.5ppm of chlorine daily - or an entire bottle. I am back to one of my original questions - this is prohibitively expensive. more than 3 times what i've ever paid for chlorine. Why am i using liquid?
 
Chaya said:
ok all. i tried again with your encouragement that the pool math HAS to work. originally i added once pump went on (about 9am) and it was sunny, so i was losing chlorine as i was adding. I got my pool paperwork and changed volume of pool the the exact 21,480 gallons on the calculator. 121 oz should raise my chlorine from 4.5 to 10ppm. 1 gallon DID raise my chlorine from 4.5 to 10 on June 15th, 16th and 17th. at end of each day it was back to 4.5. yesterday was cold, no sunshine and rainy at times. at end of day it was 5 or 5.5.

So in general i am indeed using 5.5ppm of chlorine daily - or an entire bottle. I am back to one of my original questions - this is prohibitively expensive. more than 3 times what i've ever paid for chlorine. Why am i using liquid?
Click to expand...

5.5ppm does seem a bit high considering your location. I would try doing an OCLT to make sure you don't have any organics consuming your FC.

Also, it is recommended to add your daily LC in the evening. This way the pool water is exposed to a higher concentration of chlorine for longer, provided you don't loose FC overnight. If you add LC in the morning, you start loosing FC right away to the sun.

As far as using LC vs stabilized chlorine, you have to weigh in water exchange into the equation and the ever rising CYA or calcium levels. If your CYA or calcium levels can remain in the manageable levels the whole swimming season and you are fine with exchanging water when they get too high, then stabilized chlorine can be an option for you.

Another option could be a salt water generator, but it does cost quite a bit up front.
 
We also lose 3-5ppm per day in our pool. We put a solar cover on last weekend, mostly to help retain heat and reduce water loss due to evaporation, but hoping it will also help
lower the chlorine demand. We are also looking at getting a SWCG as it will pay for itself fairly quickly with the reduced need to add liquid chlorine.
 
PoolNewb2020 said:
5.5ppm does seem a bit high considering your location. I would try doing an OCLT to make sure you don't have any organics consuming your FC.

Also, it is recommended to add your daily LC in the evening. This way the pool water is exposed to a higher concentration of chlorine for longer, provided you don't loose FC overnight. If you add LC in the morning, you start loosing FC right away to the sun.

As far as using LC vs stabilized chlorine, you have to weigh in water exchange into the equation and the ever rising CYA or calcium levels. If your CYA or calcium levels can remain in the manageable levels the whole swimming season and you are fine with exchanging water when they get too high, then stabilized chlorine can be an option for you.

Another option could be a salt water generator, but it does cost quite a bit up front.
Click to expand...
nothing in the pool, i did an overnight chlorine test a few night in a row.
i have to read up more about the salt water generator option.
 
My pool is full sun so I’ve been dealing with daily fc loss. I’m using a solar cover that basically makes the daily loss minimal. I’ve increased my cya to 50 and it seems now I’m losing about 1 ppm every two hours when the pool is uncovered. Before I felt like I was losing 1 ppm per hour when uncovered.
 

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