Top 10 hard water areas in the UK (calcium carbonate levels

[Saisonator]

I thought it was soft water for pales, hard water for stouts/porters/milds

Soft water is the best because you have almost a blank slate to start with.
You don't need to even consider acid or bottled water.

 

[strange-steve]

Thanks Steve. What I really want is a pH value, then.

No, the pH of the water has very little impact on the mash pH so you don't need to know that.

Total Hardness is given in mg/l (ppm) CaCO3.

Just ignore this, it is irrelevant.

Alkalinity is given as mg/l (ppm) HCO3.

I don't think in parts per million of Bicarb. In case anyone else does, it's 267mg/l.

You see this is why this subject can get very confusing. Your report could have values for CaCO3, hardness as CaCO3, alkalinity as CaCO3 and alkalinity as HCO3, and while those are all related, they are not the same. The value you want for brewing is alkalinity as CaCO3. If it has been reported as HCO3 as you say, then divide that value by 1.22 to convert to ppm as CaCO3.

That aside, I guess what I really want to know is why alkaline water is bad for brewing.

From Bru'n Water:
Alkalinity has a significant effect on beer flavor. Excessive alkalinity can cause wort and beer pH to be higher than desired and beer flavor can suffer. High wort and beer pH can create 'dull' flavors, harsh bitterness, and darker beer color. Conversely, when alkalinity is too low, wort and beer pH can be too low, which also affects beer flavor.