Why is the calcium hardness range so large?

[Skenn81]

Compared to all of the other recommended levels the calcium hardness range is massive, with allowable swings in the 100s compared to the much smaller targets for just about everything else.

With that being said, why is this so? What makes CH something that you don't need to target as specifically and can have it go much higher or lower over time and be okay as long as it's in that range? The difference between getting my pool to 350 compared to 550 is a massive amount of product, I could add 180 ounces or dump in the entire 50 pound bag and pretty much be fine if I need to raise it several hundered points.

Curious, that's all.

 

[Texas Splash]

What makes CH something that you don't need to target as specifically

A variety of reasons which is why TFP is so good for pools. Here are some examples:
- Location; pools in the southwest typically experience extremely high CH, so TFP and the Poolmth APP allow for compensations to prevent scale
- Water temp, somewhat linked to the item above, impacts a pool's calcium saturation index (CSI).
- Methods of chlorination; items such a chlorine tabs impact other levels such as pH. Salt cells also require special consideration to prevent scaling.
- Type of pool; we know some pools require no Ch at all, however some pool owners prefer to have a minimum level, either because a piece of equipment might state it in the owner's manual, or to prevent certain types of staining/foam.

CH is one of those items, much like TA, than can have a wide swing from left to right yet still be well managed by the pH. As such, each pool is evaluated based on its own conditions. You won't see nearly as much consideration from generic pool levels pushed by the local pool store.

 

[Newdude]

^^^^^^^^^ all of that, but also because of the # itself. 40% of 5FC is a 2 FC target range. 40% of a 100 TA is a 40 range. (60-100) 40% of a 500 CH is 200 range. 40% of a 3500 salt reading is a 1500 range.

We don't have a specific % across the board, but you can see the point that the larger numbets have larger ranges while still being OK, at a similar % in range, like salt at 3000 to 4500.

 

[Skenn81]

The % thing makes a bit more sense to me, with 40% the swing really isnt that much different than everything else. Putting it in that perspective it's the same as all the other ones. I've never actually checked my CSI in the years I have been here and doing this method. Is that something I should start? I am assuming everyone will say yes.

 

[mknauss]

Is that something I should start?

No. CSI is really only applicable to those that struggle to maintain the target ranges for pH, TA, and CH. And have a plaster pool and / or a SWCG.

 

[Skenn81]

Okay, so for the most part I have no issues with any of those. I check them, adjust as needed, and the pool just hums along. It is a plaster pool with the SWG added last year, but the levels themselves never go crazy on me as I have it running smoothly since the replaster refill last year.

 

[mknauss]

If you have no issues staying in the range of recommended levels and no issues with your SWCG, then no need to bother with CSI.