I’ve been reading that the quality of water can have an effect on the outcome of your beer. I was just wondering what kind of water I should be using (tap water, spring water, etc.)?
Not all brewing water is created equal.
Most water will produce at least a drinkable beer. However, not all waters are appropriate for all beer styles (without out some degree of modification). One can still brew any beer with them but the results are not necessarily gold medal quality.
The various famous brewing centers of world are known for their respective beer styles, in large part, due to the chemistry of their water. Through trial and error and market pressures certain regions were noted for certain styles of beer.
If your brewing water is from a municipal water supply call or write the water people and request was water analysis. They usually provided these analyses free of charge.
If you are like others and use well water then I recommend getting your water analyzed. These analyses can be a bit expensive. Fortunately, there is Ward Laboratories. Their W-6 Household Mineral Test includes pretty much all you need. It does not include iron, however. If you wish to have iron as well I would recommend getting the W-6 package plus an individual analysis of iron.
The reason distilled and RO water are generally not recommended for brewing is that they contain no minerals at all. You can add various brewing salts but these would not include minor constituents that are essential for yeast health etc. Fortunately, many of these constituents can be derived from the grain during mashing or malt extract.