CSI and CH

[Rancho Cost-a-Lotta]

Assuming the CSI level is neutral or nearly neutral and other levels are maintained within recommended ranges, are there any negative effects in maintaining a lower than recommended CH level (175-200)? Will there still be a risk of calcium etching/leaching despite the neutral CSI? Just curious.

 

[JamesW]

If the CSI is good, the CH is good.

 

[Rancho Cost-a-Lotta]

Thanks James.

 

[Richard320]

I say, "Play with poolmath."

See what happens if pH goes down to 7.2. If TA drops to 50. If the water gets up to 86F. All three. See how far outta whack it is and decide if you care about raising the CH. I probably wouldn't do anything at 175 CH knowing how fast that can climb in the summer around here.

 

[Rancho Cost-a-Lotta]

Thanks Richard. It was a hypothetical question to ensure I have a good understanding of the CH/CSI relationship. You might remember last year my CYA was in the 120-140 range with a CH of 750-800. Thanks to advice you provided, I made it through the season with clear water while managing an acceptable CSI. During the off-season, I was able to do a significant water exchange which brought my CH down to 250 and CYA down to 50 (now up to 80 after adding CYA). So things are perfect now and much easier manage. I appreciate the advice you provided.

 

[Teald024]

Assuming the CSI level is neutral or nearly neutral and other levels are maintained within recommended ranges, are there any negative effects in maintaining a lower than recommended CH level (175-200)? Will there still be a risk of calcium etching/leaching despite the neutral CSI? Just curious.

Have a look at the Pool School on CSI. By very definition, a neutral CSI means that there is no risk of calcium etching or leaching. Once you understand this concept, then you'll discover that it's a balance and adjusting of all parameters that lead to neutral CSI. There isn't one range of any specific parameter that will say if it is neutral or not.

From PS:

Simply put, CSI is nothing more than a measure of how over-saturated or under-saturated your water is with calcium carbonate. If your CSI is excessively positive, then there is a chance calcium scale could form under the right conditions. If your CSI is excessively negative, the water could dissolve (etch/erosion) calcium from any plaster source it can find, eg, your pool’s plaster and/or waterline grout. This is not an overnight process and can take several months to occur.

Also note that pH actually has the largest impact on the CSI, more than calcium does.

 

[Rancho Cost-a-Lotta]

How about high CH (800-1000) with a balanced or negative CSI? I think I've read here that calcium scaling can still occur despite a neutral CSI.

 

[pooldv]

No noticeable scaling will occur in the pool with CSI between -0.3 and +0.3 no matter what the CH level is. Ive seen people with CH in the 1200 range who have no problem with scaling because they manage their CSI. The reason we recommend a negative csi, -0.3 to 0, for SWG pools is to prevent scaling in the cell. The pH runs higher in the cell due to outgassing when it is operating. So a slightly negative csi will prevent scale in the cell and the pool.

 

[Teald024]

How about high CH (800-1000) with a balanced or negative CSI? I think I've read here that calcium scaling can still occur despite a neutral CSI.

Reread post #6 above

 

[Rancho Cost-a-Lotta]

Thank you!