Below is a post to the BeerSmith forum a couple of years ago when I was first trying out the new water tool and comparing the results with two other water-addition spreadsheets:
I took some recipes from last spring and entered them into the water adjustment spreadsheets most people use regularly. I had been using BrunWater to predict pH and have been doing a minimal of water adjustment using salts. My water is pretty bland, very similar to spring water. Only one of the recipes below contained any salt additions (the ESB with 1 gram of Gypsum for 15 liters of water). Grain bills were entered in each spreadsheet as well as each spreadsheet allows. Below are the results.
BeerSmith BrunWater EZ-Water Actual
Style Predicted Delta Predicted Delta Predicted Delta Msmt
Brown 5.45 0.08 5.67 0.3 5.46 0.09 5.37
Pale Ale 5.63 0.22 5.69 0.28 5.61 0.2 5.41
Porter 5.57 -0.02 5.69 0.1 5.57 -0.02 5.59
ESB 5.6 0.3 5.59 0.29 5.48 0.18 5.3
Average error 0.15 0.24 0.11
I don't claim any of the spreadsheets are superior or better to use. These results are based upon my well water and may not reflect what you may obtain with your process and water.
pH readings are obtained by sampling 25 cc of wort after 10 minutes of thorough stirring. Process is full volume BIAB. All batches are designed to produce 11 liters of wort at the end of the boil, approximately 14.1 liters pre-boil volume. There were no additions between mash collection and start of boil volume.
My advice: Pick one spreadsheet and use it. Measure your pH as Brad has recommended. Learn the way your water source behaves with that spreadsheet and take that into account when making future water adjustments. Remember that the spreadsheets are just estimates, relax about their exact readings versus yours, and brew on!
Note: sorry about the table, but I just cannot seem to get things to space out and line up well...