Again... more bleach?

wille

Bronze Supporter
Sep 20, 2019
45
Sarasota
I have a SWG pool and my tests call for more bleach every few days. I am increasing the SWG percentage and am now up to 35%, which is high for me. The water is very clear. I need to add some stabilizer, but before that, I thought that I'd ask the pool brains, do I need to SLAM again? 93* every day here in Florida and not a lot of rain. Thanks!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,369
Laughlin, NV
As your CYA goes lower, your SWCG will need to create more chlorine. I see that with mine.
Is your water clear? Any visible algae?
At 35% generation and 24 hour operation, you are adding 3.9 ppm FC to the pool each day. That is pretty normal for your conditions.
 

Newdude

Well-known member
Jun 16, 2019
4,584
NY
Hi Wille. The 60 CYA is probably not cutting it in the highest demand part of the season. Most of us are either 70 or 80 to protect the FC. If at any time you suspect a problem, the Overnight Chlorine Loss Test will set your mind at ease. Even with a properly oversized unit and CYA where it needs to be you may need to temporarily bump the 35% run time. Mine goes 20/40/60/40/20 with about a month at each interval. Its not set it and forget it but rather set it and it’s good for a while.
 
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JJ_Tex

Bronze Supporter
Jul 17, 2019
1,732
Prosper, TX (DFW)
In your other post, you were saying you only run for 8 hours a day. That means you are producing less than 1.5 FC daily assuming you didnt up the run time after feedback from the last time.
 
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wille

Bronze Supporter
Sep 20, 2019
45
Sarasota
As your CYA goes lower, your SWCG will need to create more chlorine. I see that with mine.
Is your water clear? Any visible algae?
At 35% generation and 24 hour operation, you are adding 3.9 ppm FC to the pool each day. That is pretty normal for your conditions.
Hi, mknauss. The water is very clear, but when cleaning the filter, it looked like there may have been algae in it. Not 100% sure, but I thought that I'd mention it. The pump is now running for 8 hours per day.
 

Newdude

Well-known member
Jun 16, 2019
4,584
NY
^^^^^^^. To clarify, I didn’t like it because I’m happy you failed. I liked because you know what to do. Technically you borderline passed but it’s too close for me personally and evidently you as well. Good job !!!
 
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duraleigh

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Mod Squad
TFP Expert
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In The Industry
Apr 1, 2007
34,437
Sebring, Florida
An overnight loss of 1 ppm passes the chlorine loss test. If your cc's are ,5 ppm or less and your water is crystal clear with no visible sign of algae, there is no reason for you to SLAM. Go swimming!
 
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duraleigh

Admin
Mod Squad
TFP Expert
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In The Industry
Apr 1, 2007
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Sebring, Florida
Keep the rest of your posts under this thread. If you post chemistry info in two different threads, it is hard to follow your "story"
 
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JJ_Tex

Bronze Supporter
Jul 17, 2019
1,732
Prosper, TX (DFW)
And once you pass the SLAM, I would suggest producing more chlorine than your current 1.5 FC you are making daily (8 hours @ 35%).
For reference, I run mine between 30 and 40% for 16 hours a day. That gives me between 2.6 and 3.4 FC daily and I adjust that about once a week depending on if my FC is high/low, expected bather load, debris in pool, weather, etc.
 
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wille

Bronze Supporter
Sep 20, 2019
45
Sarasota
I have finished my SLAM process. I would like to ask how I should properly adjust the chlorine level and the number of hours to run the pump. This is an area that I have not done properly in the past, leading to the need for a SLAM.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
7,208
Central California
I like to use liquid chlorine as part of my SWG adjusting process, unless the adjustment is minor. Here's how, after buying some chlorine.

Determine your target FC level. A lot of us like to make that at the top of the suggested range for our pool, to give us a little buffer.

Use liquid chlorine to bring your pool up to the target FC. Note the time, you'll do the following at the same time each day.

Next day, test your FC. If the FC is low, use liquid chlorine to bring your pool back up to target FC, then adjust the SWG % upwards, 5 to 10% depending on how low the FC was.

Repeat this process, every day, same time, until your FC holds.

If your FC is high, then back your SWG % down a bit, check it again the next day, same time.

The idea is to move your FC with liquid chlorine instead of trying to do it with the SWG. You'll find the correct % faster that way, because if you try to move your FC with the SWG, you'll be bouncing around with the % based on what it takes to move the FC, when what you want to know is what % is required to maintain FC. SWGs are not designed to move FC significantly, it takes them a while to catch up, which is why it can be a frustrating process without the liquid chlorine.

Hope that makes sense...

I keep a gallon or two of liquid on hand for when my pool needs a bump, like just before a big pool party, and after, or for some other event that hits my FC hard, rather than use my SWG's "super chlorinate" mode. Again, it's just faster that way, and I don't like to let my FC drop even for a few hours.
 

wille

Bronze Supporter
Sep 20, 2019
45
Sarasota
Any thoughts on how long to run the pump? The pool store told me years ago to run it 1 hour for every 10*, which would be 9 hours this time of year.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
7,208
Central California
You can use the same MO with pump runtime, too. My runtime is based on my need for solar heating, so my runtime is a constant. I don't use that for adjusting SWG production. But if you don't have any special requirements for runtime, you can use that to adjust SWG production as well.
 
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JJ_Tex

Bronze Supporter
Jul 17, 2019
1,732
Prosper, TX (DFW)
Assuming your CYA is still 60, you want to target a FC of 4, and never let it drop below 3.

Most pools are going to lose 3-4 FC daily from the sun, chlorine doing its job against debris and contaminants, etc. Since your target is 4 FC, and you can lost that much in a day, I would target trying to make 4 FC daily (you may have to adjust this later).

By my math (pool math app), your T-15 cell running at 100% for 24 hours, will add FC of 11 to your 16k gallon pool.

Knowing all of the above, you should be able to determine what run time and % for best for you. Using 4 FC as your daily production target, you can get there by any combination of % and run times including:
Pump Running 8 hours - 100% SWG
Pump running 12 hours - 70% SWG
Pump running 18 hours - 50% SWG
Pump running 24 hours - 35% SWG
 
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Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
7,208
Central California
We were writing at the same time. Runtime is determined by several factors. (But not by what a pool store says! ;) ) Let me see if I can dig up the article on that.