Agree with the above two posts entirely. Forget what the pH of the water is, but concentrate on the residual alkalinity (buffering capacity). Using calculators as a guide is fine, but if you are going to take the calculated results seriously, then you need to get serious and measure your pH even if it is with pH strips.
*pH of strike water (liquor) is not important unless it is extremely high or low (talking outside the range pH 4.5 - 9) and then there would be other problems such as high mineral-metal content that has other more significant problems than mash pH values (talking health consequences).
My town water is 7.7pH, rainwater averages around 5.5pH according to Google with some variation in local pollutants etc, so by adjusting rainwater with minerals & acids believing it was town water, I essentially reduced the pH of rainwater (ph ~5.5) to a much lower level because I believed it was 7.7. I can only assume the mash pH of the brews were below 5, or close to.
Thoughts on the above? Does this sound correct? Low mash pH isn't well covered in online articles but I can only assume it's as problematic as a high pH.
This is the problem with Googling for a solution. Yes whilst pH of rainwater is around 5.5, that is whilst it is falling from the sky. As soon as it hits your dusty/leafy roof it changes. Runs into your dirty gutters, more change. Lands in your tank (plastic, galv, concrete or otherwise), more changes. Sits there for some months/years with rotting vegetable matter, more changes. It is constantly in flux due to the environment it is in. For instance, my rain water sits in a large galv tank and was last measured a few weeks ago, with a resulting pH of 6.2. I have no doubt that the buffering capacity or residual alkalinaty of that same rain water would be sweet FA and not much of a bees appendage different if it was pH 5.5 or 7.2.
On a side note, I was at Wiesbaden, Germany a few weeks ago and they have hot springs in the centre of town, which people drink for the health benefits (It comes out of the ground ~50C). I took the attached photos of the mineral profiles, but they recommend that people drink no more than 1 litre of this stuff in any one day and not to drink it over a lengthy period. Not sure the pH value though, but the mineral content is nuts (why did I immediately think of the difficulties of brewing a beer with this water ). Note the Arsenic Content is 9 times over the recommended drinking water limit (Manganese also slightly over, but not such a problem).