Gas piping must be designed to provide enough gas to appliances without excessive pressure loss between the appliance and the meter. It is customary to size gas piping so the pressure loss between the meter and any appliance does not exceed 0.3 in of water during periods of maximum gas demand. Other factors influencing the pipe size include maximum gas consumption anticipated, length of pipe and number of fittings, specific gravity of the gas, and the diversity factor.
(C. M. Harris, Handbook of Utilities and Services for Buildings, McGraw- Hill Publishing Company, New York.)
