I understand that the water from a home Air conditioning unit is
distilled water. I wonder then if it is drinkable?

Hello declan,

I must admit I would not be too keen to try!

Information from a FAQ at the Allergy Buyers Club web site
http://www.allergybuyersclub.com/faqs/faq-ask_the_airconditioning.shtml
"Q. How does the air conditioning system inside a home become a source
of microbial contamination?
A. The air drawn into a system contains dust, much of which is
biological spores and other organic particles. Even the best filters
capture only part of this material. Much of the rest falls out of the
air stream onto the heat transfer surfaces. It combines with the water
and the spores germinate and grow rapidly"

"Contaminated central air handling systems can become breeding grounds
for mold, mildew, and other sources of biological contaminants and can
then distribute these contaminants through the home." (The Inside
Story-A Guide to Indoor Air Quality published April 1995 by the U. S.
Environmental Protection Agency).


"Air conditioning - home to deadly bacteria?
reproduced in fmuk - Facilities Management U.K. Issue -
November/December 2002
http://www.eclipsescientific.co.uk/water/legionnaires-ac.htm 

All facility managers should know that air-conditioning systems and
cooling towers are a potential breeding ground for Legionella bacteria
...  Their ability to survive and reproduce in poorly maintained water
systems has given rise to the threat of Legionnaires' disease... 
Reports show that the disease is fatal in approximately 15 per cent of
reported cases... "Over the past 3 months in our laboratory Legionella
pneumophila was identified in 82 per cent of positive samples, 21 per
cent of these were the clinically important serogroup 1."  Figures
like these show how prevalent the bacteria are in water - cooled air-
conditioning units and other water systems."

Search strategy: 1. "air conditioning" water contamination 2. "air
conditioning" Legionella

This answer to a similar question may be of interest:

http://answers.google.com/answers/main?cmd=threadview&id=237065