What is the smallest CSST gas tubing size (EHD) that can be used for a 90-foot piping system with a total pressure drop of 6-inch water column?

To determine the smallest CSST (Corrugated Stainless Steel Tubing) gas tubing size that can accommodate a piping system of 90 feet with a total pressure drop of 6 inches of water column, it's important to consider the pressure drop characteristics associated with different tubing sizes and the flow characteristics of natural gas.

The sizing of CSST is governed by specific tables and charts that indicate acceptable flow rates based on the length of the run, the pressure drop, and the gas type. In this scenario, a total pressure drop of 6 inches of water column over a 90-foot distance indicates a certain level of resistance to gas flow, and selecting the appropriate tubing size is essential to ensure that the gas can still flow efficiently without excessive pressure loss.

The chosen answer is correct because it represents a size that meets the demand of the system by balancing the flow capability against the pressure drop requirement. Tubing size 25 is able to provide sufficient internal diameter to maintain the necessary flow rates within the limitations established by the pressure drop. Using a smaller tubing size than this would risk significantly higher pressure drops, which could lead to insufficient gas supply to the appliances being served.

In summary, size 25 is appropriate for a 90-foot piping system with a specific pressure drop