If someone was to say they have a "Water Hardness of 100ppm", what does that mean?

[Stevorino]

How do I replicate that water profile? Seems like not enough info...

 

[Baja_Brewer]

IIRC, water hardness is due to calcium content. 100 ppm is likely a molar quantity. You'll need to add enough calcium to raise your content to that level.

Edit: Crap, I'm wrong. According to this, Calcium manganese and magnesium are the most common... so yeah, there seems to be something missing. I'm sure people who know water chemistry better than I will chime in, its been something I've been meaning to learn....

 

[Teromous]

It's mostly a measurement of salinity. You can buy brewers salt that contains Epsom salt, gypsum, and KCl. It's used to replicate water from different regions to get authentic tasting beers.