Who determines how clean your local water should be at?

Question

Who determines how clean your local water should be at?

Answer 1

The EPA or your state government Department of Environmental Protection (DEP) will dictate what the water quality standards will be.  It also depends on where the water is going or where it is coming from.  

If water is coming from a reservoir and then going to drinking water it wont have to go through much treatment (sedimentation, coagulation, clarification, disinfection through chloring and then storage).  

Say the water was coming from sewers and to drinking water then it would need the most intense tertiary treatment including acid base neutralization, lime scale precipitation, activated charcoal filtration and so on and so forth.  

Say the water was coming from a sewer and was getting released into a river or other water way it may just need to go through primary and secondary not tertiary.

So while the government dicates what the quality standards are the methods to achieve such standards are dependent on where the water is coming from and where it is going.  

Answer 2

The US EPA determines drinking water standards via the Clean Water Act.  Local governments may add their own restrictions.  This local autority is usually the State or County health department or it could be a state or regional water board, or a state department of environmental quality.

This is only for "community" water supplies.  If you dig your own well in your back yard and don't sell or share the water there are no restrictions other than your own common sense.