You should have your well tested once each year for total coliform bacteria, E. coli, nitrates, total dissolved solids, and pH levels. If you suspect other contaminants, you should test for those as well. You should also have your well tested if:

• There are known problems with well water in your area
  
• You have experienced problems near your well (i.e., flooding, land disturbances, and nearby waste disposal sites)
  
• You replace or repair any part of your well system
  
• You notice a change in water quality (i.e., taste, color, odor)