The hookah was a MYA QT and I agree, at some point it isn't worth it, and I reached mine. I could go back to cleaning it today and I'd still make green water. It's purely for display and spare parts now
I agree totally about vinegar being an etcher. I stopped using it for anything related to cleaning brass shells (bullets) as it eats the copper in brass and weakens the casing neck and base web over time. Diluted it works well and a soda base will stop the reaction. But in the case of this hookah, it was a last resort as an hour of scrubbing and .. yeah it got old fast.
Again, lesson learned!