The answer to 'how much to fix backflow preventer in my area' is that the cost can vary widely depending on several factors. Typical ranges for backflow preventer repair or replacement can be anywhere from $150 to $800 or more, depending on the complexity of the job, the type of backflow preventer, and your local plumber's rates.
Some key factors that influence the cost include the age and condition of the existing backflow preventer, whether it needs to be repaired or fully replaced, the accessibility and location of the unit, and any necessary permits or inspections required in your area. It's always best to get quotes from 2-3 local plumbers to compare pricing and services.