I give fresh water after a good rinsing and making sure that there is no slickness in the bowl, every day. I bleach it out every month. The breeder told me to start cleaning the water bowl and putting in fresh water every day to avoid bacterial infections after my snake regurged. He said one of his snakes got a bacterial stomach infection after leaving his water for a couple of days. If it feels slick in the bowl, it's already dirty. Even if there's nothing you can see.