I'm using ACV in my nipple waterer. I've only had it for a month so can't comment on long term affects, however I feel that it's worth it. I don't believe that the weak strength that I'm using will cause problems. Even if it does, it wouldn't be hard to change out nipples. I do strain the ACV with mother to filter out debris before adding to waterer, as I have a little concern that debris might potentially interfere with o-ring seal and cause leakage.