Hey so not really sure why to do in this situation, but the tldr long story short is that my manager used our toilet plunger to try to unclog our dish sink drain. When I confronted him on this, he said it was protocol and didn't see anything wrong with it, and wrote me off with a "well, sorry you're upset"

Longer story: for weeks I've been telling people to call in the dish sinks because when the left one drains, water rises up in the middle and right one. Up until about a week ago it wasn't terrible, just a little soap would come up from the drains, but it's gotten worse to the point where the other day the left sink drained and all three sinks rose up halfway with dirty dish water and coffee grounds. It was really disgusting and completely preventable, but whatever, it's a Saturday during rush and we have to deal with it now. My shift goes and lets my manager knows and he goes back to inspect it. I leave the room for a minute then come back in and there's a plunger in the left sink, in the murky water. I look at him and ask if that's the toilet plunger, and he says "yep! Gross right?"
At that point, me and another coworker in the room look at each other with the same WTF face, and we kinda just had to awkwardly laugh it off in the moment as our manager commenced trying to unclog the sinks with the unwashed, unsanitized plunger. I leave the room because I start to get a little upset and really grossed out, and I told a few of my other coworkers what he was doing, and I was met with equal looks of horror. But what can we do in that moment, he's the manager and we're slammed. Over the course of the next hour or two I get more and more angry and end up almost calling a health inspector in the area but decided not to because I didn't know what the repercussions would be honestly, and I'm not usually one to make big deals out of things. Other coworkers and I start to feel queasy just looking at and thinking about the state of the sink and how it's so ridiculously cross contaminated now. Eventually I decide to just talk to him, and I ask him if I can talk to him at the end of his shift.
Once we step into the back, I say that it wasn't cool to use a toilet plunger for the dish sink, that it's a really awful cross contamination and a health hazard, and that he has an example to set and that that was a poor choice to make on his behalf. He responds with direct quotes like "it's protocol," "sometimes things just get gross," "you gotta do what you gotta do," and "if you were in charge and asked me what to do I would've told you to do the same thing." I responded saying that no, I wouldn't not have done it, and I pressed him on it really being protocol to use the toilet plunger to try and unclog it, and he kept insisting that that's all he could do in the moment and couldn't understand why it upset me so much. He ended up with a halfassed "well, sorry!" and said that he's sorry it upset me, part of which I managed to record on my phone (it's super muffled though and only caught the final minute of our talk). He also said someone was going to come and unclog it and clean it, and someone did show up a couple hours later to unclog it and then left, which left the cleanup process up to us.
I'm genuinely angry about his response, how he kept insisting it's protocol, that he endangered so many peoples health by this ridiculous act, and how he couldn't see anything wrong with what he did even after I talked to him. This happened a couple days ago now, is it too late to call HR? Should I call them at all? I'm not trying to get him fired, but we all want him to at least understand that that's not cool to do.
Basically what are the next steps, is this REALLY protocol, am I crazy for being so upset?