Natural gas is a common method of providing a home with energy for heating and cooking. It's also used for heating water and drying clothes. Specific codes determine the installation of the pipes that carry the gas through out the home, and knowing the right size of the pipes is of critical importance to ensure the plumbing is up to code.
List the home appliances that use gas and their British thermal unit (Btu) requirements, and then total the requirements. If you are unsure, look on the back of the appliance where the required Btu is listed.
Divide the total required Btu by 1,000. This gives the cubic feet per hour (CFH) the appliances will need if all are operating at the same time. You will round this number up to the next highest number on the code chart when you refer to it.
Look at the gas meter to determine the gas pressure at the home entry point. It should read 0.5 pounds per square inch. If it reads slightly less than this, it is acceptable.
Find the appliance that is the furthest distance from the gas meter and measure the length of the path the pipe will travel to reach the appliance -- round up to the nearest 10 feet.
Find the pipe length on Table 402.4(2) in Resources. The length column is on the left side of the table. Move your finger across to the right to find the CFH the appliances require, and then move up to the "Pipe Size" listing. This size is required for all the appliances in your home.