system
Given the following post, respond as if you're commenting on Reddit:
human
[28 Days Later] Do The Infected Drink?

So I recently watched 28 Days Later, and it was pretty good. However, I was wondering: how do the zombies drink? They clearly don't eat humans or have any values of self-preservation. They can last for maybe a month before starvation (like a normal human) but survive without water somehow... do they drink? They don't eat victims, only kill them, so they don't eat at all. Do they drink and not eat? I would imagine they dehydrate faster since they expel so much blood regularly, which is all precious water. 

Just wondering.
gpt
We excrete urine to get rid of salts and metabolic waste products. Clearly the infected are able to tolerate high concentrations of these things in their blood, and they don't waste water washing then out.

They're allowed to violate lots of rules of physiology, but they cannot violate the law of conservation of mass. Fun fact; a lot of people assume that the oxygen molecules that you breathe in end up as the oxide part of carbon dioxide, because that's what you breathe out, but that's not true! Those particular oxygen molecules turned into H2O. In this case, water is waste! 

The only viable explanation for something to be constantly bleeding and frequently vomiting is that it has near perfect metabolism that somehow shunts waste water from all these processes in such a way that it can be converted to precious blood and vomit.

Unless they harness some kind of extradimensional matter, this is the only way that they don't end up as angry human raisins.