CSI is out of range.....should I add calcium chloride?

g4string

Member
Jan 31, 2022
7
Melissa TX
Pool Size
13250
Surface
Plaster
Chlorine
Liquid Chlorine
I have a newly built inground plaster pool. Its been filled since Jan 15. My CSI is currently at -0.42. I was wondering if I should add some calcium chloride to get my CSI somewhere between 0 and -0.3.

Here are the tests results from my last log

FC - 5.0
PH - 7.4 (a little low, but have been lowering and aerating trying too lower my alkalinity for borates)
TA - 70 (this was my target....have been working it down from 100, adding borates today)
CYA - 40 (going to add a little conditioner this weekend and shoot for 50)
CSI - -0.42

If I brought my calcium hardness to the top of the recommended range of 550-650, it would bring my CSI to a level of -0.27 to -0.34. If I am correct in my understating of pool chemistry, the calcium stays in the pool as the water evaporates. So my current level of 450 should theoretically stay the same all season. And as I add more water to compensate for the lost pool water, that hard water contains calcium as well. How much, I am not sure. So I am unsure how much extra calcium my pool will gain throughout the season with top-offs. What would you do.....leave it, or add a little calcium?
 

proavia

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TFP Guide
Feb 6, 2015
3,232
Chandler AZ
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CircuPool RJ-45 Plus
Test your fill water for pH, TA and CH. That will provide an idea of how adding fill water will affect your pool water.

If you have hard fill water, don't increase your CH by adding calcium chloride or any calcium containing chemicals.

Allow your pH to rise to 7.8 - that will also change your CSI and get it closer to the -0.30 to +0.30 range.
Don't chase the TA (or other parameters) for some magical number. And don't rush to add borates until after your CH rises a little from evaporation/refill. Since your pool is new, learn the pool first and worry about borates later. With a new finish, you pH will rise a bit faster for up to the first year.
 
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g4string

Member
Jan 31, 2022
7
Melissa TX
Pool Size
13250
Surface
Plaster
Chlorine
Liquid Chlorine
Test your fill water for pH, TA and CH. That will provide an idea of how adding fill water will affect your pool water.

If you have hard fill water, don't increase your CH by adding calcium chloride or any calcium containing chemicals.

Allow your pH to rise to 7.8 - that will also change your CSI and get it closer to the -0.30 to +0.30 range.
Don't chase the TA (or other parameters) for some magical number. And don't rush to add borates until after your CH rises a little from evaporation/refill. Since your pool is new, learn the pool first and worry about borates later. With a new finish, you pH will rise a bit faster for up to the first year.

I’m curious for the reason why you recommend to wait for borates until my calcium rises a bit?
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
3,232
Chandler AZ
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
New pool - pH rise will be an issue for up to a year with new plaster.

Don't rush to add borates. Get your plaster to cure and learn your pool. Once you do that (6-12 months), then consider borates. With borates, your pH may not rise as fast, but you will need more acid to lower your pH a given amount (7.8 to 7.4 will require more acid with borates than without).

Slow and steady wins the race. Don't be looking for a magic solution to anything pool related.
 
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Dirk

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Nov 12, 2017
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Central California
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Pentair Intellichlor IC-40
I don't use borates and never plan to. I figure the less chemicals I have to balance the better. My water looks and feels great.

Here's a tip that might help you out, both with dosing, and with understanding what dosing does. Download the Pool Math app. It goes hand in hand with the TFP method of pool care. After setting up the basic parameters of your pool, plug in your latest test results, and then find the Overview screen. Use the CSI component of the Overview section to fool around with how various chemical additions affect CSI. Specifically, raise and lower pH and watch what it does to the CSI value. You'll find that a little bump in your pH will bring your CSI into range.

This will all make better sense with the app in front of you. And if you need help, come on back and ask. We can walk you through it.

It's a great way of "adding chemicals" to see their effect, before actually adding chemicals for real.

Ha, with new plaster, which will cause pH to rise all on its own, by the time you figure out the app, your CSI will probably be just fine. When my plaster was new, it was all I could do to keep pH down. So I used the Pool Math app to help me manipulate pH (using acid) to keep my CSI dead on. It's pretty easy to do once you get the hang of it. And like you, I battled TA at first. Obsessed over it, actually. And even ignored advice I got here, because I was determined to get it where I wanted it. I got the same advice as Gene gave you, to leave it alone. But nope, I battled on. To no avail. I finally caved and trusted my TFP mentor, and left it alone. Sure enough, after a time, it leveled out where it was supposed be, all on its own. So trust Gene. Keep your pH in check, which will keep your CSI in check. And everything else will fall in line.

If you get carried away with trying to balance everything "perfectly," you might find yourself in the Yo-Yo Zone. Where fixing one number throws another out of whack. So you fix that number and some other number gets out of whack. And it's never ending. Don't go there. Trust Gene, you're in good hands.

Then, instead of fretting over numbers, pour yourself a nice drink and sit by your new pool and enjoy! :)
 
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