Help: Water Chemistry - ppm vs mg/L

**carp** · 10-10-2009, 06:31 PM

I really need some assistance regarding units of measure in water reports. My report is presented in terms of mg/L. Important numbers are:
Alkalinity 25
Hardness 23
PH 5.9
Sulfate 7
Sodium 6
Calcium 3.1
Chlorine 0
Magnesium 3.7

This is well water from the Blue Ridge mountains in VA. Some of the values (Ca, Mg) seem exceedingly low.

In Palmer's book, he presents a table of conversions to get PPM from mg/L, so my Ca level is 3.1 x 20 = 62, Mg is 3.7 x 12.1 = 45.
As far as I understand, the conversion constants above (20, 12.1) are a function of the molecular weight of the material.
Palmer's table does NOT provide ppm<-> mg/L conversion for Sulfate or Sodium.

Now on the other hand, the online chemistry calculators I have found indicate that ppm/mg/L are interchangeable.

I don't which values to use in the calculators. For example, for Ca should I be entering 3.1 or should it be 62. What about Sulfate - should I enter the value 7, or should some conversion be applied to the mg/L value to obtain the PPM value.

I'm brewing my 10th batch of IPA tomorrow and really want to optimize the water. I've liked the beer I've made so far, but feel like something is not exactly 'right' about it.

Thanks in advance,
Greg

saq · 10-10-2009, 06:43 PM

All the reading I've done indicates that PPM and mg/L are the same measurement.

Get Palmer's Residual Alkalinity spreadsheet to help calculate out your RA based on the SRM of your beer, and then tweak your SO4:CL level towards how bitter you want it to taste.

**carp** · 10-10-2009, 06:54 PM

I agree - I have the same impression. The main source of my confusion is this excerpt from Palmer:
http://www.howtobrew.com/section3/chapter15-1.html

EUREKA - I just realized that the conversion factors are from PPM to Milli-Equivalents (whatever the F that is) not mg/L. What a dolt I am. This misreading has cost me a lot of time and wasted brain effort.

Thanks