CH vs CSI Scale

[daveooph]

New pool owner. Inground, diamondbrite quartz plaster finish. I'm still balancing the water. The CSI is at
-.02 currently, but my total CH is only 60ppm due to very soft fill water. Do I need to bring up the CH to 250ish or is the csi more important then the total CH number? Looking at pool math if I bring up the CH to 250 5he csi moves to .17.

Sent from my SAMSUNG-SM-N910A using Tapatalk

 

[chem geek]

The CSI is more relevant, but how are you getting a near zero CSI with the CH only at 60 ppm? You'd have to have the pH at 8.0 and TA at 130 ppm or the pH at 7.8 and TA at 200 ppm to be near balanced with that CH. It's likely that you will be lowering your pH and probably your TA so when you do so that's when you'd need to raise your CH to protect plaster surfaces.

Also, going from a CH of 60 ppm to 250 ppm increases the CSI by 0.54 in PoolMath so I don't know how you are getting your numbers.

Is the pool literally brand new? If so, then do you know what kind of startup they are using? Perhaps they have the TA high or they expect the CH to rise from plaster dust.

 

[daveooph]

Yes the pool is new have had water about a month and they are cutting me loose this week I believe. PH is high right now at 8. Again it's high on fill water as well as the new plaster. TA is 110ppm, down from 300 ppm on the fill. I know they are adding a lot of acid trying to lower TA and PH. This will be my battle as we have to add water almost 2x a week with the high heat in Texas.

Why I ask the question is it seems to me it may be best to have a lower CH than pool school suggests. I think a CH of 200 would help keep csi near zero knowing I'll be battling high PH. Would this be right?

Sent from my SAMSUNG-SM-N910A using Tapatalk

 

[Texas Splash]

Daveooph, finding that sweet spot that is good for you by monitoring the triad if pH, TA, and CH will be a learning curve for a while once the PB gives you full rights to manage the water. Based on the Poolmath calculator , adjusting your CH to about 200 would required a TA 100 and pH of 7.6 to just about break even on the CSI scale. A little higher CH would give you more relief with slightly lower pH and TA. That would appear much more manageable than the extremely low CH version noted in post #1 which, as CG mentioned above, would require a pH of about 8.0 or TA of close to 240. Not ideal in the long run. If you are filling with soft water and plan to do so for the foreseeable future, adjusting your CH closer to the recommended level seems to be the most practical approach. Still, you might want to ask the builder some of the questions CG noted in post #2 as that may drive your choices forward. If you still have questions, please let us know. Hope this helps. Congrats on your new pool!