Massachusetts Master Plumbing Exam Prep 2025 – Complete Practice Test

Brazing is a metal-joining process that involves melting a filler metal above 450°C (about 840°F) and using it to join two pieces of metal together. In gas installations, it's important to use fittings that can provide a strong and leak-proof joint, particularly in high-pressure applications or where safety is paramount.

Concealed fittings are specifically designed to be inaccessible after the installation is complete, meaning they are typically located behind walls, ceilings, or other structures. By using brazed fittings in concealed areas, you ensure that the integrity of the joint is maintained and is resistant to potential leaks, which is especially crucial in gas installations where gas leaks can be hazardous.

In contrast, screwed fittings may be more prone to leakage over time due to the nature of the threads, and while they can be used in certain applications, they are not the preferred method for gas lines that may be concealed. Exposed fittings are readily accessible, but the primary concern with them is that they might be more susceptible to physical damage and environmental factors. Plastic fittings, on the other hand, are not suitable for gas applications due to their inability to withstand high temperatures and pressure compared to metal fittings.

Thus, brazing is used on concealed fittings in gas installations to