Losing chlorine. Is it algae?

keithpgdrb

Silver Supporter
Sep 17, 2022
101
Plainfield, IL
Pool Size
15900
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I have been having a lot of trouble keeping my chlorine up the last couple days.. My first thought is unseen algae. But when my levels started to drop, they never went below the safe range for my pool. So I should not have been growing any algae. My other thought is that the liquid chlorine bottle I had may have lost its potency. I cracked a new one tonight to see if results are the same. I’m hoping that’s all it is. I also swapped in my second set of filters. The ones in there were a little dirty. I just don’t know why algae would grow when my levels never got lower than 4. Other contaminants maybe. With the recent rain, I did have to remove some worms that had been in there.
 
I have been having a lot of trouble keeping my chlorine up the last couple days.. My first thought is unseen algae. But when my levels started to drop, they never went below the safe range for my pool. So I should not have been growing any algae. My other thought is that the liquid chlorine bottle I had may have lost its potency. I cracked a new one tonight to see if results are the same. I’m hoping that’s all it is. I also swapped in my second set of filters. The ones in there were a little dirty. I just don’t know why algae would grow when my levels never got lower than 4. Other contaminants maybe. With the recent rain, I did have to remove some worms that had been in there.
Evidently 4 is too low for your pool. Best to increase it, but depends on your CYA level.
 
What's your pump and swg schedule ? When are you testing in regards to it. A 4 might be ok if it's the low FC point of the day and the SWG immediately starts putting it back. A 4 isn't ok at the high point of the day because most SWG pools swing.

Or 0 FC rain water sat and festered for 12+ hours until the pump kicked on to mix it.

I would never run the low side of target. There's just no wiggle room to catch any unforseen events. With SWGs, most of us don't test everyday, and the unit may have been off due to low salt during a storm if the 12 hour self check lined up during a downpour. By the time you tested a day or two later, you saw a 4 and thought everything was fine throughout. On any given day it's a roll of the dice with odds in your favor the rain didn't knock out the cell for 12 hours, but over the course of a season, it can happen a few times.

Run the high side of target, as in, high target and above, for lots of safety net.

swcg_chart.jpg
 
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I have been having a lot of trouble keeping my chlorine up the last couple days.. My first thought is unseen algae. But when my levels started to drop, they never went below the safe range for my pool. So I should not have been growing any algae. My other thought is that the liquid chlorine bottle I had may have lost its potency. I cracked a new one tonight to see if results are the same. I’m hoping that’s all it is. I also swapped in my second set of filters. The ones in there were a little dirty. I just don’t know why algae would grow when my levels never got lower than 4. Other contaminants maybe. With the recent rain, I did have to remove some worms that had been in there.
I've always been told that sun or constant strong sunlight burns off chlorine. Not sure how true it was, but that's what Namco has always said and we've owned the pool since 2006. I have a chlorinator attached to my pool so I never have problems with chlorine. How are you chlorinating?
 
I have been having a lot of trouble keeping my chlorine up the last couple days.. My first thought is unseen algae. But when my levels started to drop, they never went below the safe range for my pool. So I should not have been growing any algae. My other thought is that the liquid chlorine bottle I had may have lost its potency. I cracked a new one tonight to see if results are the same. I’m hoping that’s all it is. I also swapped in my second set of filters. The ones in there were a little dirty. I just don’t know why algae would grow when my levels never got lower than 4. Other contaminants maybe. With the recent rain, I did have to remove some worms that had been in there.
Do an Overnight Chlorine Loss Test
 
My pool has an automatic cover on when not in use. So sunlight isn’t a factor in this instance. I kept my cya about 40 this season, so FC being 4 should be ok. I’ve been dozing the pool with the liquid chlorine the last couple days. I did a quick check last night before bed and the FC was up to 6.5 after adding chlorine. I’ll check it when I get home. If it’s back down again, something must be growing.

Also, I leave my pump running 24/7 with my swg set to about 7-8.
 
My pool has an automatic cover on when not in use. So sunlight isn’t a factor in this instance. I kept my cya about 40 this season, so FC being 4 should be ok. I’ve been dozing the pool with the liquid chlorine the last couple days. I did a quick check last night before bed and the FC was up to 6.5 after adding chlorine. I’ll check it when I get home. If it’s back down again, something must be growing.

Also, I leave my pump running 24/7 with my swg set to about 7-8.
Heat and time also consume chlorine.
 
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