Diminishing Chlorine Effectiveness In My Pool

0REDSOX7

Well-known member
May 7, 2018
60
Greensboro, NC
Hi all, Happy Friday!

Struggling with something here. I have a 6900 gallon above ground Intex pool. It is 18' round x 54" deep. Over the years, thanks to this website, I've learned less is more with caring for my pool, and have not had any issues since I stopped using those stupid tri-chlor tabs three years ago - and only use CYA (one time at pool opening and a refresh/addition if needed at July) and liquid chlorine.

My issue is lately, my liquid chorine is not having the same effect anymore - meaning, I need more of it to measure the same level of free chlorine. Using the pool math app and my K-2006 - I get the following.

TC - 7.0
FC - 6.5 (could be more, but I struggle with the colors here)
pH - 7.6
TA - 70-80
CYA - 50 (again, could be 40, but that Dang black dot gets me every time - I only added enough to get to 40 based on pool math, so, it's probably that, but I assume 50 for pool math calculations).

Now - pool is clean, no issues with algae or anything. Temp is around 88-90 depending on the day. I just notice that, the amount of liquid chlorine I should add (10% Pool Essentials) from the pool math app is not increasing it the level it says it should (and what it used to). I was managing my pool well by adding 4 cups of 10% every night before bed and that would keep my FC around 6.5 -7.0 - but now, it's not having that impact - and I find myself having to add 8 cups to maintain the 7.0 FC I am striving for.

The liquid chlorine is all the same date - 21-131 (May 11th) and kept inside in a closet at 72 degrees). It's clear and still smells like bleach - but, it is possible it's just simply no longer as strong as it once was? I would assume it would be okay inside for three to four months from the production date.

Again, the pool is great and I am checking every other day to keep my FC at 7.0 and no issues - but, trying to find out why now I am burning through my Chlorine twice as fast.

Thank you.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,355
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40

cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
8,648
Southern OK
Pool Size
15000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool SJ-40
Even though it is inside it is loosing strength every day, little by little... You are seeing exactly what happens when it sits... from what you are seeing it is closer to 5 or 6% chlorine now.. How many more gallons do you have?
 

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
11,190
NY
FC - 6.5 (could be more, but I struggle with the colors here)
This statement sounds like you are using the powder test to achieve the 6.5 *and* it also sounds like you are trying to decipher their yellowish color of the block test. Which one are you testing with ?
 

0REDSOX7

Well-known member
May 7, 2018
60
Greensboro, NC
Sorry - it’s the FAS-DPD powder. The colors - when it goes from pink to clear could be or drop difference I guess. Sorry for the mis-phrasing there.

So it sounds like it’s just the chlorine losing it’s strength. Would have thought it would be longer than three months.

I have seven gallons left - so essentially 14 days worth which will get me close to Labor Day, which is my target.
 

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
11,190
NY
Sorry - it’s the FAS-DPD powder. The colors - when it goes from pink to clear could be or drop difference I guess. Sorry for the mis-phrasing there.
No need to be sorry. We just need to be on the same page. :) Thank for clearing it up.

Like Marty said, it goes clear. It might even be milky-ish clear, but any kind of pink is easy to tell the difference.
So it sounds like it’s just the chlorine losing it’s strength. Would have thought it would be longer than three months.
There’s no telling what happened to it before you bought it. HD/Lowe’s/Walmart frequently leave pallets upon pallets out behind the store in the sunlight until they are ready to put it on the shelf. It could have been a little detiorated when you bought it and the time between pushed it to where you see the difference.

But.

Regualr testing gave you the heads up that something wasn’t right. And what did you do ? You made sure you kept your FC up while you figured it out. Swamp averted. Way to go.
 
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