Water Profile Tool: Conflict with Local Water Quality Report

I'm relatively new to giving a crap about my water preboil...  Until now, run tap water through a filter and call it good...

But, after a couple competition results that consistently produced negative "bitter" remarks from multiple judges, I thought I would explore all this water stuff.  (Not saying that water is definitely the culprit but my tap's pH is definitely higher than BS2's recommended range).

In reviewing my local water quality report (pdf attached), I've noticed that alkalinity (as CaCO3) is listed in the report as 43.7 ppm while the tool automatically calculates to 33 ppm - what is the formula used for this calcualtion?  Is is just algebra on the calculation shown in http://beersmith.com/blog/2016/08/10/using-the-new-brewing-water-and-mash-ph-tools-in-beersmith-2-3/?  Does anyone have any insight as to what other method my municipality would use to determine alkalinity?

Don't know if this has anything to do with it, but the Ca and Mg values I've put into the tool are the beersmith defaults for my larger metro area because the municipal report doesn't offer these measurements separately.  In the municipal report, they show "Hardness as Ca/Mg" with a value of 88.0 ppm.  The beersmith default for my larger metro area (dallas, tx) of 24 and 3 for Ca and Mg respectively don't seem to be related to the municipal report's "Hardness as Ca/Mg" metric at all.  I've contacted the water quality department to see if they can provide separate Ca and Mg measurements.

Thanks

Water supplies change, not only seasonally, but due to supply and demand as well as changes in the treatment system and other factors. It appears that your water is fairly stable according to the report you posted, but it is an old report and things could have changed a lot in the past 2 years.

If you are brewing with extract you should be using distilled or R.O. water. The brewer who created the extract has adjusted the water profile already.  If you are an all grain brewer the most important thing you need to worry about is mash pH. Your mash pH should be between about 5.2 and 5.6 ideally. Adjusting your water for brewing demands that you have an accurate starting point. None of the water calculators out there are worth a hoot unless your input is accurate.

A good starting point would be to send a sample to Ward Laboratories for testing. The information they provide in the Brewers Test will give you some real numbers to work with at an affordable price:

https://producers.wardlab.com/BrewersKitOrder.php

An alternative would be to use R.O water and adjust it as needed. Most super markets have dispensers and sell it for about $.35 to $.40 per gallon. It is close enough to distilled that you can treat it the same. Either way you have a good starting point for water adjustment. One of the pros in using R.O. is that any changes should be insignificant.