Calcite Saturation Index from Pool Calculator

[akm]

Greetings...

Now that I'm getting a handle on water balance, I'm curious if shooting for 0.00 on the CSI from the Pool Calculator is ideal...it seems like it but maybe not?  Perhaps I'm doing it wrong.

I seem to have stabilized at:

pH: 7.6
TA: 60
CH: 150
Borates: 50

That is leaving me at -0.15 CSI at 100 degrees Fahrenheit.

As an OCD perfectionist, should I keep tweaking to try to hit 0, or is CSI not instructive for spas?

Thanks!

[Topline Mike]

Your numbers and my numbers are darn near identical.  I wouldn't do a thing to your water balance, close enough to a zero csi reading.  Notice if you change your goal CH to 240 or so, you get nearer to zero.  Chem geek says that a CH of 150 is best for no foaming. 

You are using dichlor/bleach method, correct?  Adding bleach won't change your numbers.  If you were using bromine with the floater and the tablets in the floater, your pH would slower go down little by little, because the tablets are net acidic. 

You've got it nailed down, akm, now all you have to do is enjoy the hot tub!  Good work.

[akm]

Will do dichlor then bleach, but I've failed to lay in any bleach so far so I'm staying with dichlor for the near-term.  Will be re-filling after a month anyhow, so I'm not sweating the CYA yet.

Seemed like things were pretty tight, but it's like playing a game and I want the "high score" lol.  Definitely enjoying it though - was away for 4 days for the holiday and was back at it tonight.  Happy days indeed.

[chem geek]

With an acrylic shell tub with no exposed plaster or grout, there is no need for having the CSI be near zero.  That is only to protect surfaces containing calcium carbonate.  You want to be careful not to have the CSI too high since that can result in scaling and with the large amount of aeration in hot tubs the pH can get high pretty fast.  So a lower CSI is safer to prevent that.

When you do switch to Dichlor-then-bleach, don't forget to add the 50 ppm borates (usually using boric acid) before you switch to bleach.  That will help to keep the pH more stable.

[H823Putt]

How do I know how much to add to get 50ppm? I have a 380 gallon tub. I just changed my water over the weekend and was thinking of doing the dichlor then bleach

[chem geek]

The Pool Calculator is no longer supported.  The original creator has now made PoolMath that he supports so I'd use that.  For a 380 gallon tub, 50 ppm Borates can be added from 15 ounces weight (16 ounces volume) of granular boric acid which you can get at DudaDiesel or The Chemistry Store.