The Danbury Water Department is warning customers of a drinking water standard violation that occurred earlier this year.  Although not considered an emergency, water samples during July showed that turbidity measurements, or cloudiness, exceeded standards.  The violation did not require customers to take corrective action such as boiling water, but the Danbury Water Department noted that compromised immune systems, infants, and some elderly may be at increased risk of nausea, cramps, diarrhea and associated headaches.  The water quality in the reservoir improved within a few days resulting in a return to normal turbidity levels.