I need to know whether it is ok to put into a birdbath, water that has been...
Hello and thank you for contacting Ohio State University Extension Ask an Expert. We had done a through search to identify if softened water is a concern in a birdbath. While we didn't find any specific concerns, consistently the recommendation is to use fresh water. Fresh water could be collected in a rain barrel or from a ground well. Public municipality water can be used since the treatment water is not a concern in birdbaths.
Cornell Lab of Ornithology has a nice reference on Providing Water for Birds
I also received a message from the OSU Extension Wildlife Program Specialist and she shared "softened water should NOT harm the birds. So no need to use non-softened water."
So you don't have to go to a lot of trouble to avoid softened water in a birdbath.
Bruce, I do so appreciate you sharing with me the response from the wildlife program specialist in particular. I care very much for the birds I feed and provide water for; a friend had made an issue about harming them with the water I use for them. I am so relieved! Thank you. Martha Horn
My pleasure to assist. I'm grateful for you contacting Ohio State University Extension - Ask an Expert.
You're welcome, Bruce. And I would like to add that the public is so fortunate to have a resource such as this to assist with questions and give the sound advice that you do. Hope you'll all always be there for all of us! We need you! Martha Horn