Dear Shrikant,

We can't convert TDS into meq/l, but we can for majors elements.

For piper diagram try diagramme it's available in web site of university of avignion.

Best for you

Yes i agree with Mr.Elgattafi. Its easier to convert major elements from ppm or mg/l to meq/l as the conversion is possible with following equation:

meq/L = (mg/L) / EW (where, meq/L = milliequivalent per liter, mg/L = milligram per liter, EW = equivalent weight)

yes i have gone through it and it works. thanks for answer