Natural Gas Pipe Sizing in 90 Seconds
If your furnace runs but the house never quite gets warm, the problem usually is not the furnace. It is the gas line feeding it.
What this covers
An undersized gas line starves every appliance downstream. Here is how to size one right, using just three numbers. Number one.
The load. Add up the B-T-Us of every appliance on that line. Furnace, water heater, range.
That is your demand. Number two. The length.
Measure from the meter to the farthest appliance. Use that one length for the whole system. Number three.
The pressure. Standard homes run about seven inches of water column, with a small allowable drop. Take those three numbers to the code sizing table.
Find your length, read across to your B-T-U, and it gives you the pipe size. Get it right and every appliance gets exactly what it needs. Get it wrong, and you will chase problems for years.