Split from this topic. JasonLionDave, don't be so quick. Here's some coffee. @[_]~~~ Saturation indexes are important, especially to those in areas with high CH in the fill water.

Scott

I don't think I understand that. What saturation indexes are important? How does TDS figure into them?

Higher amounts of charged ions (a higher TDS) lower the CSI. The pool calculator includes this effect in the calculation when the salt level in used in the calculator. A pool with a salt level of 3,200 ppm will have a CSI about 0.19 lower than a non-salt pool.

We're wandering further away from OP's original thought but I want to be clear in my mind that TDS is not relevant to CSI calculations....correct?

Additionally, it is my understanding that CSI calculations themselves are not necessary if you keep your pool within the guidelines suggested here on this forum.

TDS does affect the CSI. The pool calculator uses the salt level for the TDS when calculating the CSI. A pool with a salt level of 3,200 ppm will have a CSI about 0.19 lower than a non-salt pool.
My opinion is that the CSI is important. How important depends on the specifics of the pool. Some people do not consider it very important or helpful.

In practice there is almost never any point in measuring TDS, even for calculating CSI. As long as you know the salt level, which is usually the great majority of the TDS, you will get results that are more than close enough.

Jason, thanks for splitting that off. I really would hope we can keep the "spirit" of BBB which is simplicity. Adding TDS into the mix to calculate a CSI value (which I find very dubious to begin with) just seems to further complicate our forum and make the simple unnecessarily complex.

JmesW, I can't find a need in my water chemistry management for CSI. I know what it is and I know where it should be (roughly) but I never seem to find a case where it reveals anything to me that I don't already know. I only keep my CH and pH and TA within the suggested levels we prescribe here on the forum and that seems to suffice.

I think I understand that a pool with abnormally high CH and no hope of lowering it may find CSI useful but isn't it just as simple to run pH and TA at the minimum suggested values to compensate? I am not trying to be obstinate but I am somewhat possessed about keeping the website simple so newbies aren't drawn into complexities they don't understand or need

The TDS effect is small enough to just treat it as a "salt pool" vs. "non-salt pool" sort of binary decision. However, I wouldn't ignore it completely. Though -0.2 isn't a huge amount, when combined with other aggressive ranges it can just make things worse. The Pool Calculator already has an entry for Salt where a "0" or any entry lower than what is "implied" by the TA and CH values is automatically accounted for. So if someone knows they have a salt pool, they just put in 3000 ppm in the Salt entry in The Pool Calculator and the calculator will do the rest. It's really not more complicated for anyone and isn't really any different than putting in the CYA level where the calculator automatically adjusts the TA for the saturation index calculation.

So I agree that people don't need to go out and get conductivity meters or test strips for TDS. Just roughly measure your salt level or just go with the binary category and you'll be fine.

I agree that things should be kept as simple as possible. I think that the CSI should only be referenced if it is necessary. In most cases, the poster does not need to worry about the CSI as long as they follow the guidelines.