Beer is made up of over 90% water making it the ingredient we use the most the therefore should not be overlooked. Most municipal water sources are treated in one way or another and by a general rule is perfectly okay to use in brewing however knowing the mineral composition can help produce better beer and beer that is true to style.
Calcium added to the mash can lower the pH and is used when brewing pale ales. It keeps the yeast healthy and the beer clear.
When added to the mash chloride brings out the sweetness of the malt. It also adds a fuller mouthfeel.
Used to lower mash pH it is naturally occurring in barley therefore can add more depth to the final beer.
When added in brewing it brings out the sharpness and bitterness of hops. This can be good for some styles, not so good for others.
Depending on the quantity of sodium in the water it can enhance sweetness or make a beer taste salty.
Acceptable in darker style beers like stouts it helps to round out the roasted flavours and bitterness of the malt while creating a creaminess. Used in lighter style beers it can make the hops flavour too harsh.
When found in water it can create off flavours in beer. It will be similar to a Band-Aid like, antiseptic taste.