Oklahoma backflow testing rules
Oklahoma DEQ rule OAC 252:631 (Public Water Supply Operation) applies to any person or entity operating a Public Water Supply system, except minor systems regulated under OAC 252:624.
Who sets the rules in Oklahoma
OAC 252:631-3-17(b)(1) (amended eff 9-15-25): PWS systems shall not allow a physical connection between a drinking water line and a line carrying water of unknown or questionable quality.
OAC 252:631-3-17(b)(2): an air gap of at least 6 inches or two pipe diameters, with a reduced pressure zone backflow device accepted in lieu of an air gap. Fire suppression systems are not treated as hazardous supplies.
OAC 252:631-3-17(b)(3) and the matching construction rule OAC 252:626-5-15(a)(3).
OAC 252:626-5-15 Cross connections and interconnections is the design-standard counterpart; it says to avoid cross connections in the system.
Both rules require diversion line with equal backflow prevention and no pit or vault placement.
Sources: OAC 252:631 sets operating standards for public water supply systems; Construction standards (OAC 252:626-5-15) repeat the cross-connection limits for new works
Which properties need a backflow preventer
OAC 252:631-3-17(b)(2) and 252:626-5-15(a)(2): a fire suppression system is not a hazardous supply for the purpose of the air-gap/RPZ requirement. No state testing mandate for fire lines found.
Source: Fire suppression systems are not considered a hazardous water supply
Common questions
Is backflow testing required every year in Oklahoma?
Oklahoma DEQ rule OAC 252:631 (Public Water Supply Operation) applies to any person or entity operating a Public Water Supply system, except minor systems regulated under OAC 252:624.