According to NFPA 750 2019, copper tube used in water mist systems must be Type L.

According to NFPA 750 2019, copper tube used in water mist systems must be Type L.

• A. False
• B. True
• C. Type K
• D. Type M

Answer: (B)

The main idea is that piping materials for water mist systems must have enough wall thickness to reliably handle the system’s pressures. NFPA 750 2019 specifies copper tubing for water mist as Type L. Type L copper has a thicker wall than Type M, giving better hydrostatic strength and resistance to pressure surges, while still being easier to work with and less costly than Type K. This combination makes it the appropriate choice for indoor water mist piping, where the system operates at moderate to high pressures but doesn’t require the extra thick walls of Type K. Type M is too thin for typical fire protection pressures, which can risk leaks or failure. Type K, while the thickest, is generally reserved for underground or special high-pressure applications where such robustness is needed, and it would add unnecessary cost and rigidity for standard indoor water mist runs.

The main idea is that piping materials for water mist systems must have enough wall thickness to reliably handle the system’s pressures. NFPA 750 2019 specifies copper tubing for water mist as Type L. Type L copper has a thicker wall than Type M, giving better hydrostatic strength and resistance to pressure surges, while still being easier to work with and less costly than Type K. This combination makes it the appropriate choice for indoor water mist piping, where the system operates at moderate to high pressures but doesn’t require the extra thick walls of Type K.

Type M is too thin for typical fire protection pressures, which can risk leaks or failure. Type K, while the thickest, is generally reserved for underground or special high-pressure applications where such robustness is needed, and it would add unnecessary cost and rigidity for standard indoor water mist runs.