Code | UL-1738 Listing

While polypropylene vent pipe may carry a slight material premium, installers typically save up to 70% on labor because UL 1738–listed polypropylene vent systems install much faster. The overall cost of installation is often lower when using UL 1738 polypropylene vent pipe compared to alternative options.

InnoFlue® Polypropylene Special Gas Vent Systems, tested and listed to UL 1738, have been sold in the United States and Canada since 2009. In Europe, polypropylene flue gas vent pipes have been in use for over 25 years, proving themselves to be a safe, reliable, and industry-standard technology.

Yes. Centrotherm’s InnoFlue® Polypropylene Special Gas Vent Systems are fully approved by the Massachusetts Plumbing Board. This means UL 1738 vent pipe can be confidently installed in compliance with state plumbing and safety regulations.

PVC is not used in Europe as a flue gas vent material because of its lower maximum operating temperature and environmental safety concerns. Instead, Europe relies on polypropylene vent pipe, including UL 1738–listed systems, which offer higher heat resistance, improved durability, and greater safety margins for condensing appliances.

InnoFlue® UL 1738 vent pipe is available at numerous plumbing and HVAC suppliers across the United States and Canada. Installers can easily source UL 1738 polypropylene vent pipe from regional and national distributors.

Polypropylene flue gas vent systems are specifically engineered for the application. Polypropylene has a vicat softening temperature (the temperature at which the thermal plastic deforms under load) that exceeds 300⁰F. This allows the safe use of InnoFlue® Polypropylene Special Gas Vent Systems to sustained temperatures up to 230⁰F, after subtracting the 70⁰F of safety margin. Condensing heating appliances (furnaces, boilers, tanked water heaters and tankless water heaters) are typically designed to have flue gas temperatures below 150⁰F when operating at optimum efficiency.

System design (inclusion of base board in hydronic systems or use of multiple zones in furnace systems), building owner comfort (higher reset temperatures), required 180⁰F hot water or a lack of routine field service (operating with scaling on the heat exchanger or clogged filters) can cause heating systems to generate flue gases in excess of 200⁰F.  Schedule 40 PVC “is intended for non-pressure applications where the operating temperature will not exceed 140⁰F.”* At 140⁰F, PVC has only 22% of its original design strength remaining.

*Per the Charlotte Pipe Schedule 40 PVC Submittal Document.

Yes. Over the past eight years, all major heating equipment manufacturers have listed polypropylene, including UL 1738 vent pipe, as an approved material in their installation manuals. Industry groups such as AHRI and HARDI support polypropylene adoption, and states like Massachusetts, New Hampshire, and provinces like British Columbia have restricted PVC in favor of UL 1738 polypropylene vent pipe.