Watts LF757DCDA DOSY GPM 4 Part of the LF757DCDA Series Sheet Drain This 3 4 inch lead free This 3 4 inch lead free reduced pressure zone backflow preventer assembly with its exclusive design incorporating the patented air inch and water out principle for protection during an emergency condition prevents the flow of polluted water from entering into the potable water supply due to backsiphonage and or backpressure This 1 2 inch reduced pressure zone assembly backflow preventer helps prevent the flow of polluted water from entering into the potable water supply due to backsiphonage and or backpressure in accordance with national plumbing codes and water authority requirements Non health hazard application but not toxic