Good Morning.

Water practices and policies on board airliners are not the same across the board even in the USA.
For my part I have only been drinking bottled water on board airplanes for the past 10 years.
As it relates to drinking water in 40 years of flying I have never tasted as bad a glass of water on a plane as I did yesterday on USAIR#79.
This was my experience.
I indicated it to the flights attendants to no avail and was not offered a glass of cool good tasting water unless I paid up.
I am including a link to the EPA site discussing airlines water safety here:
http://www.epa.gov/safewater/airlinewater/index2.html
When you look at the shape of some of the planes flying the skies today as well as the latest lack of maintenance records reported a few months back I am not sure safe drinking tap water is really a #1 issue with the unfriendly skies.