Which is the appropriate schedule for pipes measuring 1-1/2 inches or smaller?

The appropriate schedule for pipes measuring 1-1/2 inches or smaller is Schedule 40. Schedule 40 is commonly used for a variety of applications because it provides a good balance between strength and weight. It is typically recommended for most residential and commercial piping systems due to its ability to handle various pressures while still being manageable to install.

In contrast, Schedule 10 has thinner walls and is used primarily in low-pressure applications. Schedule 80 features thicker walls than Schedule 40, making it suitable for high-pressure situations but might be considered overkill for standard applications in small diameter pipes. Schedule 20 is not commonly used and is often perceived as less robust compared to Schedule 40.