Old regulators should work satisfactorily with the new ACME OPD valves assuming that the appliance rating in BTUs does not exceed 100,000 BTUs per hour. If the appliance has a maximum output rating of over 100,000 BTUs per hour, the smaller orifices in the design of the ACME OPD valve may result in some restrictions in the vapor flow from the tank. A regulator that is not working properly should be replaced with a new one. For further assistance, please call our Customer Care Center at 1.800.BLU.RINO.