Here's what makes the dog situation worse than cats, and why almost nobody talks about it.
Cats evolved in deserts. Their survival depended on extreme water selectivity. A cat's sense of smell is roughly 14 times more sensitive than a human's, and they use it to screen every water source before they drink. If something smells off, they walk away.
Dogs evolved as scavengers. A dog's sense of smell is 10,000 to 100,000 times more powerful than yours. They can absolutely detect the chloramine and heavy metals in your tap water. But they drink it anyway.
Dogs have no evolutionary instinct to refuse contaminated water. They smell it. They register it. And they drink it because their DNA tells them to consume available resources before they disappear.
Every single day, your dog walks up to their bowl, smells chemicals that shouldn't be there, and drinks the entire thing because they trust that you've given them something safe.
Meanwhile, those contaminants are accumulating in their kidneys, liver, and bladder. Mineral deposits build up. The filtration tissue scars over. Function drops quietly, year after year. By the time bloodwork catches it, three-quarters of the kidney is already gone. That tissue doesn't regenerate.