http://lifehacker.com/5844191/
Back in 2008, I put a note in my computer to come up with a Web site to provide a Q&A exchange with doctors on basic questions about health... looks like HealthTap beat me to it and they did a great job! I asked a question a half hour ago and it was already answered by two doctors! Here is my question with answers below:
How long can I use the same water bottle before washing or acumulating harmful bacteria?
Dr. Robert Kwok answered:
Wash it twice a week
A healthy person using a water bottle to carry clean drinking water is unlikely to get an illness from "harmful" bacteria in the bottle. Neither the water nor the bottle are sterile, so there will be some bacteria, but probably won't cause disease. Rinsing the bottle with a little drinking water at each refill will help keep the bottle clean. Actual cleaning of the bottle can be done twice a week.
2 minutes ago
Dr. David Finke answered:
Less than a week1st answer
First, make sure the bottle is BPA free and avoid reusing commercial one-time use water bottles over and over. Keep the water bottle out of hot environments and rinse it frequently. I wash mine with soap and water every 2-3 days.