Chlorine mystery, new pool

MrPSS

New member
Feb 2, 2022
4
Tampa, FL
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-20
Hi everyone! Love this group and the TFP methodology.

I just can’t seem to avoid adding chlorine to my new pool. Link to all my logs are here. I’ve done my best to keep accurate logs so you can see what I’m dealing with.

Background: Pool build completed Christmas of 2022. Normal 30 day start up from the builder. After 30 days they added salt and turned on the salt cell (intellichlor ic20). After 2 months running it on the cell 100% and maintaining with liquid chlorine and me testing like a madman every day wondering where the chlorine has gone every 2-3 days I did many tests and took my water to several different pinch a penny and Leslie’s to test for phosphates, metals etc. Nothing of concern came up in their tests. No phosphates ever— we don’t have them in the city water someone told me. The builder then determined my cell was bad and replaced the cell about a month later.

Now: I accidentally flooded my pool by leaving the water running overnight and so this provided me with the opportunity to start from nearly scratch on salt and cya. This was about 5 weeks ago when my new salt cell (ic20) was installed . My cya was under 30 and salt around 3200 after this event and so I added about 5lbs of cya over the course of a week and a half to bring it up to around 60/70 and also added a bag of salt which now has me around 3800-4000 on salt. The cell says maintain 3600 and all the right lights are always on. The new cell was installed March 29th and now here we are 5 weeks later and I’m still dealing with the same /similar issue. I have my pump running 8hrs a day with the cell at 100% and I still need to add at least 64oz or more of liquid chlorine every 3 days or so because my chlorine will get down to 1 and 2. Id like to mention that through this entire time my water is crystal clear and only begins to get cloudy if I don’t manually add liquid chlorine. Oh and I also tested that the new cell is producing chlorine by testing the water away from jets and then water directly from the jets and the chlorine level is nearly 1ppm higher at the jets!

I’ve also tried using only main drain and skimmer for circulation thinking maybe I had poor circulation with the cleaner always going but that didn’t really help either.

Please see my logs mentioned above and all my equipment details in my signature below. Any and everyone I talk to about this whether at a pool store or my dad who knows a lot about pools are all baffled by the fact of where 3+ ppm of chlorine can go over the course of 24 hours and why my chlorine will not stay in the pool, even though I have my cell running at 100% for sufficient time each day. One pool guy even told me my chlorine should be through the roof running it at 100% all the time and adding that much liquid chlorine together.

Any help or guidance is appreciated. I’m also going to upload a screenshot of a recent test from Leslie’s.
 
Pss,

An IC20 is way too small for a 15K pool. You really need an IC40.

Your IC20 only makes .26 ppm of FC per hour. 8 hours at 100% is only 2.1 ppm per day.

Let's see what some of our other members have to say..

Thanks,

Jim R.
 
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+1. If anywhere needs their SWGs to be particularly oversized, it's the hot climates.

My poolmath defaulted to 100% / 24 hours and the IC20 will produce 5.6 FC a day in 15k gallons. You'll need to run it most of the (24 hour) day, most of the season.

With all the times your FC dipped below minimum per FC/CYA Levels, you could have a nascent algae bloom being held at bay by the SWG. No SWG can overcome the exponential growth cycles once alge gets in there.

2 things consume FC. UV from the sun, and organics (in this case, algae). So we run an Overnight Chlorine Loss Test to remove the sun from the equation. If you lose FC overnight, it's algae, and time to SLAM Process.

If you pass, you'll need considerably more runtime going forward. We see pools average 2-4 ppm loss a day over the season, with the 4 usually coming in the peak season. You're Tampa May is like my NY peak season.
 
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+1. If anywhere needs their SWGs to be particularly oversized, it's the hot climates.

My poolmath defaulted to 100% / 24 hours and the IC20 will produce 5.6 FC a day in 15k gallons. You'll need to run it most of the (24 hour) day, most of the season.

With all the times your FC dipped below minimum per FC/CYA Levels, you could have a nascent algae bloom being held at bay by the SWG. No SWG can overcome the exponential growth cycles once alge gets in there.

2 things consume FC. UV from the sun, and organics (in this case, algae). So we run an Overnight Chlorine Loss Test to remove the sun from the equation. If you lose FC overnight, it's algae, and time to SLAM Process.

If you pass, you'll need considerably more runtime going forward. We see pools average 2-4 ppm loss a day over the season, with the 4 usually coming in the peak season. You're Tampa May is like my NY peak season.
Lol try here 😂😂 we aren't even hitting normal temps and I'm already averaging a 5.5-6 fc loss a day
 
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Excellent, so this is very helpful all! Now that I suspect this is the problem, what is the best scientific way for me to pitch these findings to my pool builder to get them to now replace a 2nd salt cell for me, being this one is too small for my pool? I know they're going to fight me on this and so I will have to do some fighting myself in order to prove to them my case of them under sizing my SWG.
 
Show him the pool math outputs and point out where you live. Yours would be plenty to get by in Michagan, but iffy at best in Tampa.
 
I’m also in Florida (though farther north, on the east side of the state) and I had a similar issue with not holding chlorine. My build was also finished right before Christmas and couldn’t hold chlorine after the salt cell was turned on. Now my SWCG is rated for a 40k gallon, I think, but everyone was telling me I shouldn’t need the output higher than 10% in February and I had to crank it way up to get it to hold. Long story short, my issue was a nascent algae bloom. I performed the SLAM and now my cell is set at 15% for 11 hours a day (poolmath says that is 1.1 per day) and my chlorine level is actually on the high end at 10.5ppm with little movement. I’m not saying your cell isn’t undersized, but you should definitely also consider that you have something growing in the water.
 
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+1. Hands down, Overnight Chlorine Loss Test to see if theres more than one issue going on.

After passing an OCLT or completing a SLAM, then it's much less of a rush while adjusting things going forward. Right now, you could be losing ground by the hour on a one way trip to swampville.
 
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