AP MEJ400 Brass Liquid Level Vent Valve 1/4" NPT Propane

The AP MEJ400 is a brass liquid level vent valve designed for propane and LP gas systems in RVs, trucks, and industrial applications. This standard vent valve helps operators safely detect liquid levels when filling propane tanks and effectively bleed down connections before disconnecting transfer lines.

Key Features:

• 1/4 inch Male NPT connection for easy installation
• All-brass construction for durability and corrosion resistance
• Standard #54 orifice size minimizes product loss during operation
• Knurled stem completely unscrews from valve body for easy stem replacement
• Compatible with Marshall Excelsior globe valves (ME815-X series) and angle valves (ME825-X series)
• Installs into downstream auxiliary port on transfer valves
• Made in the USA

How It Works:

Install the vent valve in the vapor space of the tank. Open the valve before filling begins to allow vapor discharge. When the tank reaches maximum liquid fill capacity (80% of tank capacity), liquid will begin to discharge from the vent valve, indicating the tank has reached safe fill capacity. The valve also verifies that transfer system valves have closed properly—opening the vent valve until liquid or vapor stops venting indicates it is safe to disconnect.

This is the standard emission version. For reduced emissions, consider upgrading to the low-emission or self-cleaning models. The MEJ400 is also known as Propane Vent Valve #72 in some applications.