This article is from the Water for coffee FAQ, by Jim Schulman with numerous contributions by others.
The alt.coffee archives have answered almost all my coffee
questions. However, the coverage on water problems seemed a little
less than complete. So I'm adding this bit of research as a small
repayment for all the help I've gotten here. It's too long to read in
one sitting, so copy and peruse it at your leisure. Headings and
subheadings are in block capitals; you can find what you need by
scrolling through. There are several tables, so use a fixed pitch
This is not meant to be the authoritative word on water
quality for coffee, I don't have nearly the expertise for that. I'm
hoping to acquaint readers with enough information and sources so that
we can argue water matters as proficiently as other coffee issues.
There are bound to be mistakes in here, so I welcome all corrections.
This FAQ covers the effect of minerals in natural waters on
coffee taste and coffee makers. It has four sections. The long first
one explains how to measure scale related water properties and how to
estimate scaling rates in espresso machines based on these. The
second looks at water treatments. The third taste tests espressos made
with variously treated waters. The fourth puts together the
conclusions of the first three and outlines water treatment and
The FAQ does not discuss water impurities such as chlorine,
organic materials, or heavy metals, since they shouldn't be in any
drinking water, and since they're removed by all water bottlers,
reputable types of water filtration, and municipal water boards.
Municipal levels of chlorine are removed by charcoal filtration,
letting the water stand two hours, or heating it. If your waterboard
uses chloramines for disinfection, the water should be charcoal
filtered prior to taste sensitive food use, since these do not
dissipate on their own.