school me on CSI please

[ocmagnum]

Ladies & Gents,

Been reading a lot of posts regarding CSI and been "modeling" on the pool math app to see what impact CSI in what way, but still struggle a bit to understand how I can get my CSI number closer to 0.

Here are my numbers from last night:

FC 4.5
CC 0
pH 7.5
TA 80
CH 225
CYA 60 (previously at 40, added stabilizer two nights, so that number might go up slightly over the week)
Salt 3800
Temp 71
CSI -0.57


So the obvious one is that CH should come up a bit. But even if I put it right in middle of target at 400 on pool app, it only moves the CSI to -0.330. Raising pH also appears to lower CSI quite a bit (according to my playing with pool math), but would need to be at over 8 to get to 0 CSI, so not really desirable. All other results appear to be in range, so I'm not clear what lever to pull to assist getting CSI to as close to neutral as possible. Or should I just not worry about it too much if all else is in range?

Thanks in advance!

 

[triptyx]

That doesn't look right to me.

Putting in the same numbers, I'm getting -.56, which is close to the bottom of where you want it.

Colder water has a significant effect on this number. Leave your CH alone, but let the pH come up to around 8 while the water is cold. As it warms up, you can start targeting around pH 7.5.

In general, especially when the numbers are very close to suggested (as yours are), keeping the pH between 7.2 and 8 will be just fine for your plaster. Where CSI really starts coming into use are in places such as the desert southwest or where the water is very hard and people are trying to minimize scale with CH numbers in the high 100s to 1000 or more.

 

[ocmagnum]

Thank you so much Triptyx!

You are absolutely right, my result was -0.57, typo on my end.

 

[triptyx]

No worries! If you're worried that you're too close to -.6, just let the pH naturally rise to around 8 and then maintain it there. I believe that takes you to around -.08 (if memory serves) which is darned near balanced at that water temp.

Does your fill water have a reasonable amount of calcium in it? If you can expect evaporation to cause that CH number to go up over the season, it's fine just where it is. If not (or your fill water goes through a water softener), you might consider adding a little calcium to the water to assist that CSI number a hair.