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If the error message says, 'non-numeric data', then you have strings (i.e. letter-and-space sequences) or other non-numeric data present for sure, in some field referenced by your script, program, or procedure.
The cure is either to state the non-numeric data as 'typed' i.e. to state its data type, e.g. String, etc. Somewhat in this fashion, vaguely:
String phvalue1 = "Acidic";
(I am using somewhat Java-like syntax in that statement.)
...or the other cure, is to not reference the non-numeric or String-type data, in your calculations.