Total Chlorine less than Free Chlorine ?

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Joined: Sat 23 Jul, 2011 00:41
My Pool: 42,000 Liter (8m x 4m) coffer and liner construction with 'All in One' pump/filter unit.
Location: France

Total Chlorine less than Free Chlorine ?

Postby TimboZero » Sun 31 Jul, 2011 02:22

Hello All,

Yesterday I replaced my SWG and whilst I was at the shop I had my water tested. They used a automated precision pipette to measure water into individual test 'cells' that were pre-dosed with the testing chemical and sealed (obviously this seal was broken to add my pool water). Each 'cell' was then measured in a photometer. I would expect this to be as accurate as testing could be outside of a lab.

the results were :-

pH 7.4
FC 2.89
TC 2.08
TA 90
CH 170
CYA 40
Salt 4000

This is for a SWG chlorinated pool and I would consider that the CH and CYA should be raised a little ?

The thing that surprises me (and I dont understand) is how the TC is less than the FC ? surely TC=FC+used chlorine and would always be slightly higher than FC ?
Is this an indication of another problem , a testing error or perfectly normal ?



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My Pool: 16 x 32 gunite21000 gal., Diamond Brite Blue, Swimquip XL pump, DE36
Location: Texas

Total Chlorine less than Free Chlorine ?

Postby czechmate » Sun 31 Jul, 2011 21:34

Looks like your La Leslie's store is as dependable as some around here in the US.
Anybody can make a bad test.
What is much worse is, that he than puts absolute nonsense on the paper.
Your CYA is very close to ideal level. If you feel like raising it let some trichlor float in the floater.
Your FC is barely high enough anyway.
drain and refill

Total Chlorine less than Free Chlorine ?

Postby drain and refill » Mon 01 Aug, 2011 08:52

when you have a salt pool their manuels normally state to keep your cya/conditioner at 80ppm so you dont burnout the cell as fast. Also check your manuel as salt is suspose to be 3200ppm and when to high the cells will shutoff.
chem geek
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Total Chlorine less than Free Chlorine ?

Postby chem geek » Mon 01 Aug, 2011 12:14

Just make sure that your FC level is at least 5% of the CYA level, so if the CYA is 80 ppm then your FC should not be lower than 4 ppm. Otherwise, algae can grow faster than chlorine can kill it (regardless of phosphate and nitrate levels).

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