The answer to 'how to clean backflow preventer' is to regularly inspect and clean the backflow preventer to ensure it is functioning properly and preventing contamination of the water supply. Backflow preventers should be cleaned and tested at least once a year, or more frequently if recommended by the manufacturer.
To clean a backflow preventer, first turn off the water supply and relieve any pressure in the system. Then disassemble the device, removing the check valves and any other components. Use a soft-bristle brush and mild detergent to clean all the parts, removing any debris or buildup. Rinse the parts thoroughly and inspect them for any damage or wear. Replace any damaged components, then reassemble the backflow preventer and turn the water back on, checking for any leaks.