CSLB Class B General Contractor's License Practice Exam

What is the best way to prepare a pipe when brazing or soldering gas pipes during the installation of water heaters?

1. Clean it with water

2. Blow into the pipe using your lungs

3. Clean the surface using a power tool

4. Use a pressurized air canister

The correct answer is: Clean the surface using a power tool

Cleaning the surface of the pipe with a power tool is the most effective method for preparing it for brazing or soldering. Proper surface preparation is essential to ensure a strong, leak-free joint. When using a power tool, such as a wire brush or a grinder, you can effectively remove any dirt, rust, and oxidation that may be present on the metal surface. This creates a clean metal surface that allows the brazing or soldering material to adhere properly. Welds and joints require clean surfaces to ensure proper fusion between the metals. If the surface is contaminated, it can lead to weak joints, which may eventually fail or leak. Additionally, certain standards and codes necessitate a thorough cleaning process when working with gas pipes to ensure safety and reliability in installations involving flammable gases. Other methods of cleaning, such as blowing into the pipe with your lungs or using household water, do not achieve the level of cleanliness required for effective brazing. Using a pressurized air canister may remove some debris but is often insufficient for removing tougher contaminants like grease, rust, or oxidation, and might not ensure a proper clean surface for the joint. Power tools provide the necessary abrasion to address these issues comprehensively.