The answer to 'how much to fix backflow preventer' is that the cost can vary widely depending on several factors. Typical ranges for backflow preventer repair or replacement can be anywhere from $200 to $1,000 or more, depending on the complexity of the issue, the type of backflow preventer, and the labor required.
Some key factors that influence the cost include the location and accessibility of the backflow preventer, the need for any parts replacement, the complexity of the repair, and the hourly labor rate of the plumbing professional. It's essential to get local quotes from licensed plumbers to get an accurate estimate for your specific situation.