I was thinking ACVabout metal waterers - I've used galvinzed metal waterers in the warm months for more than a decade and a half and never had any problems . RIght now, given it is still winter (more snow tonight and below freezing, but warming up tomorrow) , I'm using the plastic inserts in heated water bowls. And the last couple of years have had glass so I can use acv, but still have used the metal waterers in parts of the run so that there is always multiple water sources.
having trouble seeing the metal waterers as a health problem.