Hardness Question

Hypothetical question.

If I have a pool that according to the Saturation Index is at 0.0 for perfectly balanced, but the calcium hardness of the pool is 800ppm, is there still a possibility for scaling since it's above the recommended 400ppm? Also, at what ppm of calcium will water not be able to dissolve anymore calcium?


TFP Expert
LifeTime Supporter
Jun 7, 2011
Midland TX
Welcome to TFP!

Yes, depending on what else happens in the pool sure it's possible, and with less than 800. Scaling is dependant on more than one factor. Not assuming you don't realize that, but it needs to be said. I don't know the answer to your second question, but whatever that value is, it's impractical to apply it to any likely pool scenario. Maybe you're just a curious sort like me, so I'm curious why you ask that.
May 14, 2017
League City, Texas
I work around pools that have higher calcium levels but still fall into acceptable ranges on the saturation index and wanted to see if it was safe as long as they fall into acceptable ranges on the saturation index?


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
I deal with this constantly with my pool. You can still get scaling in areas with poor water circulation. It's not too hard to keep the CSI neutral up to about 800 CH, but as the water gets warmer, your ability to tweak pH and TA to keep it there gets smaller and smaller. And of course, CH is going to keep creeping up. It's time to start replacing some water.