Sign to warn tourist about water

Solution 1:

Only 2. and 4. are incorrect or unidiomatic. ("Untested" or "uncontrolled" would be more correct.)

However I don't think any of the choices given are a good under these circumstances.

Vaguely describing the status of "control" or "testing" is far too indirect an approach for communicating a safety concern. What would you be testing or controlling for anyway, temperature? pressure? I know you're talking about pathogens or chemical contaminants, but I work for an engineering firm that builds water treatment plants. I wouldn't expect that knowledge from the general public.

I would say: "Water may contain organisms that can cause disease." or "Water may contain arsenic which may cause poisoning." or something like that. Then follow up with "Drink at your own risk."

Solution 2:

I would go for untested water. The term water testing exists. The Planet Magazine has a post about it which says:

Before you stoop for a drink at Western’s untested water fountains, ask yourself, is it really worth it?

It has this picture with a detailed notice, saying:

Water testing results pending mitigation completion. Please use other sources for drinking until further notice.

If there is a risk, it is better to be explicit about it, rather than concise.

You could also say water not tested, though sometimes this expression requires a continuation (for lead, by a laboratory, etc.)