Maxitrol Vent-Limited Line Pressure Regulators w/ OPD (5 PSIG Systems)**VENT LIMITER INCLUDED** Maxitrols 325 L Series with overpressure protection devices (OPDs) are CSA certified (ANSI Z21. 80 CSA 6. 22) for up to 5 psi inlet pressure, and 7 to 11 inches w. c. outlet pressure (see page 18). The L models with OPDs are for use on piping systems up to 5 psi such as CSST (corrugated stainless steel), semirigid copper tubing, or steel black iron pipe. The regulators reduce pounds pressure to a level within the appliance or