Introduction to Cation/Anion Balance (CA Balance)

Water that is potable (drinkable) should be electrically neutral.  This is determined by taking into account results from the following analytical testing: pH, conductivity, total dissolved solids, and other analytical tests that determine major cationic and anionic constituents.  Ratios are looked at between calculated results and actual analytical results.  When outcomes are outside of the expected ranges, reanalysis is required to bring the CA Balance closer to closer to neutral (which may not be possible).  Laboratories use the CA Balance to determine if they have conducted their analytical testing correctly.

What does it mean?

If your water is potable then the CA Balance is a good way to verify that the laboratory testing was done well – as long as your report includes the above testing methods.  If your water is not potable then the CA Balance is more useful the cleaner the water you submitted is.  If your water is contaminated, then there is no analytical purpose for reporting or conducting a CA Balance.

Why is it important?

It is important because many analytical reports will provide CA Balance results.  Most people don’t understand that the CA Balance is really only useful when looking at pristine water. Standard Methods discusses a 5% acceptable/working range for potable waters.  SVL uses guidelines around 10% to help us with testing semi-clean waters.  The information helps our project managers to requests reanalysis of the test that may have led to the unbalanced results.

How does it show up in SVL’s work? What’s an example of where it can be used?

When looking at an SVL report, if requested the CA Balance results will show up under the heading: Cation/Anion Balance and TDS Ratios.  It will report the cation sum and anion sum in meq/L, The C/A Balance in %, the calculated TDS number, and the TDS/calc.TDS ratio.

What should you beware of?

Something to watch for is how many tests have been reported, because you could be missing key components to the CA Balance if you haven’t requested all of the tests required for a good balance.   Different industries have slightly different takes on the type of balance they are looking for.

Where can people go for more information?

https://ndep.nv.gov/uploads/documents/2009-cation-anion-balance-guide.pdf