RoseMary, Different size HN's??? I never have seen any mention of different sized HNs. Hmm. Please tell me more, if you can direct me to the same kind you are using, I'd sure appreciate it.
As for the thickness of the container's walls, it had a pair of screw-in cups, which I replaced with these HN's.
Thank you also for the tip on ACV's corrosive nature, given its high acidity. I've also read about putting anything pure copper in the water to circumvent algae. Algae is my primary point of adding ACV, as years ago when we had a couple hens I fought algae constantly and never heard of ACV being added to the water back then. Weird that I missed that back then, but anyway... If you have any suggestions on how to avoid algae growth, besides daily washing of the waterer, I'm ALL EARS.
@imnukensc as far as different sized horizontal nipples. I just use whatever came with my waterer, I would guess different manufacturers make different sizes, but I don't know for sure.
Knowing now that you replaced the drink cups with horizontal nipples makes me think that the leaking is between the wall of the waterer and the nipples. It can possibly be that the wall isn't thick enough for the nipple attachment to form a good seal or the hole where the nipple is threaded through is slightly too large and allowing a slow leak there. Not sure if there's a good way to figure out which exactly is the problem. You could try putting some thread seal tape on the threads or some sort of sealant around the opening to see if that stops the leaking (make sure whatever you use is safe for drinking water).
So as far as ACV and algae... I don't get algae. I also don't use ACV or any other additives in the water. I've always used fully opaque waterers kept in the shade, and that's enough to stop algae growth in moderate temperatures. I don't even clean my waterers other than a quick rinse out, as they don't need any attention other than that.