TDS and Saturation Index

[PoolGuyNJ]

Split from this topic. JasonLion

Welcome to the forum :lol: You will have no application at all for the TDS meter. TDS is irrelevant to pool water chemistry. As poojguynj mentioned above, you really need a drops-based test kit to accurately test your water.

Pool School has several articles including "ABC's of Pool Water Chemistry" which will get you headed down the right path.

Dave, 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

 

[duraleigh]

Re: How to determine CH from TDS reading

Saturation indexes are important, especially to those in areas with high CH in the fill water.

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

 

[JamesW]

Re: How to determine CH from TDS reading

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.

 

[duraleigh]

Re: How to determine CH from TDS reading

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.

 

[JamesW]

Re: How to determine CH from TDS reading

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?

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.

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.

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.

 

[JasonLion]

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.

 

[duraleigh]

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

 

[chem geek]

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.

 

[JamesW]

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.

 

[MoreSparkle]

I see this is resolved... But if you all would indulge a newbie.... Does having a lower TDS level say anything about the current water quality... I understand it's not a necessity, and am not suggesting pool owners start worrying about measuring it.. I just happened to see it on the one and only sample I took to a local hardware store that does testing... I do my own testing with a Taylor k 2006, but was curious what they would tell me.. Can anyone comment on the TDS relationship to water clarity / quality? If one were to care, what would be considered a good level?

Just curious....

 

[chem geek]

The TDS tells you nothing about the quality of the water. TDS is mostly salt. So unless you start out with high salt level, it's mostly a measure of how much cumulative chlorine (and possibly some other chemicals) that you have added over time (less any dilution of the water). You can generally ignore it.

Some pool stores measure it because they believe that it is what causes water to have problems, but it's usually the CYA level that is getting high from continued use of Trichlor tabs which makes the chlorine less effective allowing algae to grow.