**Sample interview questions:** Can you explain the process of sizing gas lines for high-pressure or high-flow applications?

**Sample answer:**

**Determining Gas Line Size for High-Pressure/Flow Applications**

**Step 1: Calculate Gas Flow Rate**

- Determine the maximum gas usage (in cubic feet per minute or CFPM) of all gas appliances connected to the line.
- Use manufacturer’s data sheets or industry guidelines to estimate CFPM for each appliance.
- Calculate the total gas flow rate by adding the CFPM for all appliances.

**Step 2: Determine Pressure Requirements**

- Identify the pressure requirement of the gas appliance with the highest demand.
- Use manufacturer’s specifications or the International Gas Code (IGC) to determine the minimum operating pressure.

**Step 3: Select Gas Line Material**

- For high-pressure applications (>5 psi), use Type L copper or CSST (corrugated stainless steel tubing).
- For high-flow applications, choose gas lines with a larger internal diameter (ID).

**Step 4: Apply Sizing Formula**

- Use the following formula to determine the minimum inside diameter (ID) of the gas line:

`ID = (CFPM * 30) / (P * 0.6)`