Help with Pool Math

[tmarcoux]

Hi all,

I have been a BBB convert and loving it. The pool looks better than ever and is easier to maintain - so Thank You!!!

I do have a question regarding Pool Math. I enter in my readings and follow the recommendations. When I hover over the CSI value, it shows "Balanced"; however, I was entering numbers in the various fields to understand the effect of changes onto CSI, and when I changed all of the numbers to match the TFP recommended ranges, the CSI read "Potential to become corrosive to plaster". My question is why, if I was in perfect range of the recommendations, would my CSI not be balanced?

I attached a screen shot of Poolmath

Just curious.

 

[duraleigh]

I won't be able to answer your question, but I will say that CSI is not applicable to 99% of the conditions of pool water management.

It serves a purpose in some rare conditions but I am of the opinion it causes far more worry on TFP than it helps.

 

[JasonLion]

To really understand what is going on, you need to take into account how the PH is likely to change, which PoolMath can't do. When you are following our recommendations, PH might well go up, but it almost certainly won't go down much. While CSI has the potential to get too low, the way the chemistry is adjusted there is hardly any chance of that actually happening.

 

[tmarcoux]

Thanks for the quick reply. I have to admit that I was watching it too closely. I will continue to stick with the guidelines.

 

[jblizzle]

Just to add, the picture you posted still have the CSI in range. Note it would need to be below -0.6 before you might start to have issues, although I think it needs to be even lower.

 

[chem geek]

I brought up this issue two years ago in the thread Saltwater Chlorine Generator (SWG) Recommended Levels where I proposed some minor changes to the recommended levels to bring up the CSI somewhat (note that my CSI numbers use my accurate spreadsheet so are slightly different than that calculated in PoolMath varying by only 0.03 or so). It's difficult when there are recommended ranges since you can have a larger swing depending on the specific values, but it is true that at the worst extremes for the current recommended levels one can get to a CSI of -0.7 which is pretty low. The recommended levels are supposed to give a CSI for SWG pools that is somewhat negative (around -0.2 or so) and that is intentional to reduce the risk of calcium carbonate scaling in the SWG cell. At any rate, TFP did not end up changing the recommended levels.

Note that experiments by onBalance show that the risk is dependent on the quality of plaster that is used and how it is applied (i.e. what the plasterer does with making the plaster and the conditions during start-up). With well-made plaster, it is resistant to corrosion from a lower CSI especially if that is due to parameters other than low pH. However, with poorly made plaster, it can show signs of trouble starting at -0.6 in his experiments.