Gas Meter Terminology?

Question:In determining gas line sizing for adding a tankless hot water heater I have ran into some terminology that I need some help with. wc differential and drop, Have seen it listed as 1/2",1",and 2" How do these relate to calculatig the capacity of the meter itself?

Answers:
WC Differential is Water column which is the measurement for pressure. Drop is how much pressure you are going to lose over a length of gas line. the national gas code book has how to calculate this. Depending which trade does the gas piping in your area a plumbing or heating company will be able to determine this for you. Otherwise contact your local gas utility for information. Being that tank-less water heaters run at pretty high BTUs, you might even have to get your gas meter re sized.