What is the purpose of the rain cap?

• A. To minimize the entrance of water or extraneous matter into the relief device or discharge piping
• B. To redirect rainwater away from the site
• C. To regulate vapor pressure
• D. To seal the relief device completely

Answer: (D)

The rain cap’s job is to keep rain and other debris from getting into the vent path of the relief device and discharge piping. When propane systems vent, the path must stay open so gas can escape safely if overpressure occurs. A rain cap is there to shed precipitation and block large objects, but it must not create a complete seal that would stop the vent from doing its job. If the cap sealed the relief device completely, it could trap gas and prevent relief during overpressure, which is dangerous. The cap’s purpose is about protecting the venting path from water and debris, not about redirecting rain or regulating vapor pressure, which are handled by other parts of the system.