Originally Posted by maxvolume
Would the water Ph effect AG more than partial mash?
It's not the water Ph, but the Ph of the mash, and yes it can effect an AG much more than a PM. When you say partial mash, how many pounds of grain are we talking about, and how long was it mashed? Many of the PM batches I see only use a pound or two of specialty grains, and get most of the sugars from extract. They also often have a much shorter mash. Four to twelve times the amount of grain, and a much longer mash would amplify any water ion concentration issues greatly.
A quick internet search shows bicarbonate levels in San Fran for 2008 to vary between 12.2 and 117 ppm, with an average of 61 ppm. Beersmith estimates an SRM of 14 for the recipe you posted, which would mean that ideally you'd want the bicarbonate levels to be under 50 ppm.
Not only does the water vary quite a bit throughout the year where you live, but it probably also varies depending on what part of town you live in. It is very likely that the water you used for the AG batch had more than the desired amount of bicarbonates. If your recipe had included a few darker malts, you probably wouldn't have noticed any issues at all.