46 CFR §58.16-16

1. (a)All systems shall be provided with a regulating device so adjusted as to release gas to the distribution tubing at a pressure not in excess of 18 inches water column, or approximately 10.5 ounces per square inch.
2. (b)The low-pressure side of all regulators must be protected against excessive pressure by means of a suitable relief valve, which must be integral with the regulator. The relief valve must be set to start to discharge at a pressure not less than two times and not more than three times the delivery pressure.
3. (c)All reducing regulators must be fitted with a pressure gage located on the high-pressure side of the regulator.