638-105

This 4" to 5" B-Vent Increaser is a critical component for optimizing exhaust flow in gas-fired heating systems. Designed to transition seamlessly from a 4-inch diameter vent pipe to a larger 5-inch diameter system, this adapter ensures proper drafting and safety for residential and commercial HVAC applications. Engineered for use with Type B gas vents, it is ideal for connecting appliances like water heaters, furnaces, and boilers to a larger common vent or chimney liner. The double-wall construction provides excellent thermal insulation, protecting surrounding combustible materials while maintaining high internal temperatures for efficient exhaust removal. Whether you are performing a new installation or upgrading an existing ventilation system, this durable metal increaser provides a secure, leak-resistant fit.
Type: Metal Venting / B-Vent Adapter
Size: 4 inch to 5 inch
Dimensions: Standard B-vent fitting length × 5-inch outer diameter × 4-inch inner diameter inlet
Application: Used in gas-fired appliance exhaust systems including furnaces, boilers, and residential water heaters. Specifically designed for Type B double-wall gravity-vented systems.
Specifications: Double-wall construction, corrosion-resistant galvanized steel or aluminum outer casing, secure locking transition from 4-inch pipe to 5-inch pipe.