Pool Chemistry makes my head hurt.

MyWifesPool

New member
May 10, 2025
2
Chesterfield, VA
Pool Size
17300
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-20
When our pool was installed a few years ago, we were told by the installer to test and monitor chlorine, alkalinity, and salt on a weekly basis. Fast forward to last summer and our blue, beautiful, shimmering pool had morphed into an ugly and chalky looking mess.

After some back and forth with the installer, it was determined that we hadn't been paying attention to the LSI of the pool water and that caused severe scaling on the gelcoat. The installer eventually offered to have the pool resurfaced with ecoFinish. The pool looks great, but now achieving and maintaining the proper LSI has become the biggest pain in my...

I've been using an LSI calculator in an effort to balance my pool, but the chemistry ranges are way off from ecoFinish's recommended ranges. Can someone please help me figure this out before I sprout anymore gray hair?

I tested my water this morning, and below are the results:
FC & TC - 0 ppm (SWG was on lowest setting, have since set it to 20%)
pH - 7.2 ppm (aimed returns up to help aerate water)
TA - 160 ppm (added 1/2 gallon of muriatic acid to start to reduction)
CH - 170 ppm
CYA - 36 ppm
Salt - 3500 ppm

I'll test again tomorrow, but any and all help would be appreciated.

Thanks in advance,
Ant
 
Last edited:
Welcome to TFP.

This has nothing to do with LSI but you need chlorine in your pool ASAP.

Your CYA is 40. I don't know how you measured 36, but we round up, so if the dot disappeared between 40 and 30, you call it 40.

Get your FC up to 5-7 and you may want to do a Overnight Chlorine Loss Test to check if algae got into your pool while your FC was low.


1746922306761.png

As to LSI, we use CSI with PoolMath


Download PoolMath, turn on CSI Tracking during setup, and enter your values to calculate your CSI.


 
Last edited by a moderator:
  • Like
Reactions: MyWifesPool
Welcome to TFP.

This has nothing to do with LSI but you need chlorine in your pool ASAP.

Your CYA is 40. I don't know how you measured 36, but we round up, so if the dot disappeared between 40 and 30, you call it 40.

Get your FC up to 507 and you may want to do a Overnight Chlorine Loss Test to check if algae got into your pool while your FC was low.


View attachment 644944

As to LSI, we use CSI with PoolMath


Download PoolMath, turn on CSI Tracking during setup, and enter your values to calculate your CSI.


Thanks. To be honest, I don't know why I wrote 36 ppm in my notes. As for the chlorine, should I wait fir the SWG to do it's job? Or should I add 2 bags of sodium dichloro-s-triazinetrione to the water?
 
As for the chlorine, should I wait fir the SWG to do it's job?

Nope. Your IC20 is too small for your 17K pool to begin with/

By the time it raises your Fc, you can have an algae problem.

Or should I add 2 bags of sodium dichloro-s-triazinetrione to the water?
The best way is to add 1 gallon of 10% liquid chlorine, which will raise your FC by 6 ppm.

30 oz of Dichlor will raise your FC by 7 ppm and another 7 ppm of CYA in case you already have algae and need to follow the SLAM Process.
.
 
Last edited by a moderator: