Hi NH,
That may be the culprit. We do have some mineral concentration in our water. Thanks for reminding me!
you could likely send it into a lab to get a more detailed analysis. You could simply use pH papers to determine the acidity to begin with.
you can buy a plastic type waterer instead. For the winter you would need a heater or de-icer that is rated for use in Plastic. But, last year my experience with this is as follows: use electric de-icer made for use in plastic buckets...first morning of below freezing temps find bucket iced and the horizontal nipples not working due to ice. So remove non-working item, put another brand-new-out-of-the-box-full-price-item into bucket...next morning same thing-frozen water. And this is inside an enclosed coop that is elevated and plugged directly into an electric outlet (no extension cords). So, we moved to the heater option (rated for 5 gallon buckets). Wow!!! That was very warm water, but birds drank it until a few days later when the wire cage started to rust in the water, and it kept getting worse. We tried a variety of solutions, but birds would not drink this warm/hot rusty water-even when fresh.
so we ended up using a plastic heated dog bowl. Perfect.
This year, we have more birds. So, we will use the metal heater base sold for use with these galvanized waterers. Hopefully that works. If not it’s back to the heated dog bowl.