One thing I never thought about as a new brewer was water. As it turns out water is very important. Did you know that 90-95% (by weight) of beer is water? Even though it seems obvious, you probably never gave it a second thought.
How many recipes do you see that call for a specific a water type? Not very many, unless it was written by an advanced brewer or is for a very specific beer style.
When I lived in northern Nevada, all my beers had a common flavor. The beers I made developed a "lime" flavor. It drove me crazy! I cleaned, re-cleaned and paid extra attention to sanitizing but nothing worked and it would not go away.
I moved to Colorado where the water is much different and behold, that "lime" flavor disappeared! What happened?
Turns out a high pH (that is a measure of acidity in water) will do that. The lime flavor comes from a pH approaching 12 ppm (parts per million). The ideal range is 6.5-8 ppm. Most municipal water supplies fall in that range, but it turns out, Nevada has a very high pH in their water.
All this leads up to the fact that water matters a great deal. Let's look at some other water issues you may or may not know about.
The big one is chlorine! Every municipal water supply uses it to drive off germs and bacteria. That is fine for swimming pools (where even more is added), but what does it do to beer? Have you ever heard someone say, "That beer tastes like old Band-Aids?" The taste you are getting is called chlorophenolics. It has a flavor that tastes at best like medicine, and at its worst tastes like Band-Aids. How do you make sure there is no chlorine in your water?
1. Use all store bought spring water. It is not chlorinated, and all excess ozone is destroyed before bottling.
2. Boil your tap water then let it cool back down before adding steeping grains (works for chlorine only). Some say let it sit overnight before using.
3. Add ½ a crushed Campden tablet (or 1/16 teaspoon of metabisulfite) per 5 gallons cool water, stir in and let stand 5 minutes. NOTE: Not advisable for people who can not tolerate sulfites (wine makers us it as a preservative).
How do minerals get into water you ask? Minerals are naturally found in soil. Soft rainwater makes it down through the soil, through underground caverns, over rocks in streams or aquifers where it picks up some of the following dissolved minerals along the way.
h) Trace metals such as iron and copper
An entire book could be written on water and water chemistry, but that really is getting pretty advanced. I would encourage you to do more research as you become more familiar with the craft of home brewing.
Each of the minerals listed affect water and brewing in a different way. Without getting too technical, we will just say for now that different water chemistry works better with certain beer styles. For example, waters low in alkaline are known to be better for lighter styles of beers, like English Bitters, where water with higher concentrations are better for stouts and heavy beers. It is also known that very soft water, water with sodium being the only trace element, is better for Pilsners and light beers than hard water containing many more trace elements.
The water used for extract brewing is not as critical because your malt has already been mashed. Therefore you do not have to worry about the mash pH, and are only concerned with flavor impacting minerals like sodium, chloride, magnesium and sulfates.
So you ask, "Is there a way to tell if your water is sufficient for brewing?"
My rule of thumb (interesting origin to that phrase by the way) is this: taste the water, really taste it! Make sure it is at room temperature (taste buds lose effectiveness below 46 degrees Fahrenheit). Does it taste good? To tolerate it do you have to chill it? Is there a salty or lime flavor to it? If you detect anything at all that tastes off, your taste buds are telling you something. Either go purchase a minimum of 6 gallons of filtered water, or boil it out and taste it after it cools. If it still tastes bad, buy your water making sure it tastes good as well.
Now you can see why water is important.