Public or Private there are things you should know.  How to clean a well?  How about bacteria in public water?  Metals or VOCs ?  Some of these links will help point you in the right direction  Do your research. 

Water & Lead Removal

There is a lot of material out there.  There are all kinds of filtering methods.  Be sure the method you are considering can substantiate the claims it makes.  From my reading whatever the method, it should have the NSF (national Sanitation Foundation) seal on it.   Do your research.  

County and Local Water / Well regulations.

This is what we have learned so far.  this is not implying that this is the last word on legal or compliance.  It is always advisable to verify whatever you find here.  This simply gives you an idea of what the expectations may be from your community