SWG Chemistry

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T

TPOOLJ

0
Sep 7, 2014
4
Chester Springs, PA
First I just want to reiterate how informative this site is. I just installed a new IG pool last year and I am already more expert on water chemistry than others I know who have had pools all their life. I must say my new pool has indeed been TROUBLEFREE!!!

My pool was completed late in the season last year so I waited until this season to put in the salt and start up the SWG. I have also followed the SWG chemistry recommendations from this site. My question is that at these recommended levels the Saturation Index in PoolMath is consistently mid-range negative. Meaning around -.3 to -.4. Is this intended? If so why is balanced (index = 0) not good for a SWG?

Thanks, I'm just concerned about leaving it in negative territory all the time.
TpoolJ
 
Those numbers will be perfect and will not degrade the plaster. What they will do is help keep the cell from forming scale and not reducing its lifespan due to the need to clean it with acid when scale forms.
 
The water chemistry inside the cell is very different than the bulk pool water. The biggest difference is that the pH is a lot higher inside the cell as the generation and low solubility of hydrogen gas drives up the pH. So, even if your bulk pool water is -0.3, inside the cell is probably closer to 0.

Can you post your latest test numbers? I'd like to see why your CSI is so negative.


Sent from my iPhone using Tapatalk
 
The Recommended Levels relating to the CSI for an SWG plaster pool are as follows:

pH 7.6-7.8 ..... Mid-Range: 7.7
TA 60-80 ..... Mid-Range: 70
CH 350-450 ..... Mid-Range: 400
CYA 70-80 ..... Mid-Range: 75
assume Salt is 3000 and Temp is 80

The CSI in PoolMath with the above is -0.14 so where are you getting -0.3 to -0.4? Even if I were to use the mid-ranges in PoolMath set up for "troublefreepool.com", "SWG", and "Plaster" which has pH 7.65, TA 70, CH 300, CYA 75 I get -0.31 so is that what you are talking about? We made changes to the Pool School Recommended Levels tightening up the pH range and moving up the CH range and these changes have not been made to PoolMath yet.
 
THANKS EVERYONE!
Here are my current numbers
FC 4.2
TC 4.3
PH 7.8
TA 77
CH 240
CYA 75
It looks like I should raise my CH. I was around 300 at closing last year, but I had some scale over the winter (new pool was open for only 60 days before closing) that dissolved on its own within weeks of rebalancing/opening. However my Calcium from my readings and the pool store have consistently been around 240 this year and I've been hesitant to raise it because of the scale last year...but I've been told that was because the finish was so new still. I've also kept the PH consistently between 7.6 and 7.8...I'm a little anal about keeping the pool balanced.
Thanks again for all you help and comments...I've referred a good number of new folks to this site as well.
TpoolJ
 
-0.3 is not a serious problem. We changed the Recommended Levels not so much for the mid-range, though that should be closer to -0.2 for SWG pools, but rather for the low-end of the range (except for CYA at the high-end) since that was too low before pushing -0.7
 
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