InnoFlue® UL 1738 vent pipe systems provide safe, reliable, and proven polypropylene flue gas venting. Explore our FAQ to learn why UL 1738 polypropylene vent pipe is the industry standard for high-efficiency furnaces, boilers, and water heaters.
In most cases, using UL 1738 polypropylene flue gas vent pipe does not increase overall installation costs and can actually reduce total project expense. While the material cost of UL 1738 / UL1738 vent pipe may be higher, the system is designed for faster, simpler installation.
UL 1738 vent pipe systems typically feature lightweight components, gasketed or locking connections, and fewer required fittings, which helps reduce labor time on the job. Because UL 1738 vent pipe is specifically listed and approved for high-efficiency appliances, it can also minimize inspection issues and rework, saving time and money.
When labor savings, code compliance, and long-term durability are considered, UL 1738 polypropylene vent pipe often provides a lower total installed cost compared to non-listed venting alternatives.
InnoFlue® polypropylene UL 1738 vent pipe has been available in the United States and Canada since 2009. These UL 1738 listed polypropylene vent pipe systems have a proven track record in North America for safely venting high-efficiency heating appliances.
In addition to their North American history, polypropylene flue gas vent pipes have been widely used in Europe for more than 25 years, where they are considered a safe, reliable, and industry-standard venting solution. This long-standing global use demonstrates the durability and performance of UL1738 vent pipe technology in real-world applications.
Yes. InnoFlue® UL 1738 vent pipe is fully approved by the Massachusetts Plumbing Board. Centrotherm’s InnoFlue® Polypropylene Special Gas Vent Systems, tested and listed to UL 1738, meet all applicable state plumbing and safety regulations.
This approval allows UL 1738 vent pipe to be confidently specified and installed throughout Massachusetts for approved gas-fired appliances, helping ensure code compliance, inspection approval, and long-term safety.
PVC is not used as a flue gas vent system in Europe due to its lower maximum operating temperature and environmental and safety concerns when exposed to hot, acidic flue gases from high-efficiency appliances. These limitations make PVC less suitable for long-term flue gas venting applications.
Instead, Europe has standardized on polypropylene vent pipe systems, including UL 1738 listed polypropylene vent pipe, because they provide higher heat resistance, improved chemical durability, and greater safety margins. UL 1738 vent pipe is specifically engineered to handle the temperatures and condensate produced by condensing boilers, furnaces, and water heaters, making it a safer and more reliable venting solution.
This long-standing European adoption has influenced North American codes and manufacturers, leading to the increased use of UL1738 polypropylene vent pipe as the preferred option for modern, high-efficiency gas appliances.
InnoFlue® UL 1738 polypropylene vent pipe systems are widely available through plumbing and HVAC suppliers across the United States and Canada. Installers and contractors can source UL 1738 vent pipe from both regional distributors and national supply houses, making it easy to obtain for residential and commercial projects.
Because UL1738 polypropylene vent pipe is a listed and commonly specified venting solution for high-efficiency appliances, most major HVAC distribution networks either stock InnoFlue® products or can quickly order them as needed.
UL 1738 polypropylene vent pipe is specifically engineered for flue gas venting from high-efficiency, condensing heating appliances. Polypropylene offers superior thermal performance, chemical resistance, and long-term durability compared to non-listed vent materials.
Polypropylene has a Vicat softening temperature exceeding 300°F, which is the temperature at which a thermoplastic begins to deform under load. After applying a 70°F safety margin, InnoFlue® Polypropylene Special Gas Vent Systems, tested and listed to UL 1738, are approved for continuous operation at temperatures up to 230°F.
Most condensing furnaces, boilers, tank water heaters, and tankless water heaters are designed to operate with flue gas temperatures below 150°F when running at optimal efficiency. However, real-world conditions can increase flue gas temperatures beyond this range. Factors such as hydronic system design (including baseboard heating), multiple heating zones, higher temperature reset settings for occupant comfort, required 180°F domestic hot water, or reduced maintenance (such as scaling on heat exchangers or clogged filters) can cause flue gas temperatures to exceed 200°F.
By comparison, Schedule 40 PVC is intended for non-pressure applications where operating temperatures do not exceed 140°F. At 140°F, PVC retains only 22% of its original design strength, significantly reducing its safety margin for flue gas venting applications.*
For these reasons, UL1738 polypropylene vent pipe provides the correct combination of temperature resistance, safety margin, and code compliance, making it the preferred and listed material for modern flue gas venting.
*Per the Charlotte Pipe Schedule 40 PVC Submittal Document.
Yes. The HVAC industry is well-established and highly familiar with UL 1738 polypropylene vent pipe, and it fully supports the transition away from PVC for flue gas venting applications.
Over the past eight years, all major heating equipment manufacturers have listed polypropylene venting materials, including UL 1738 / UL1738 vent pipe, as approved options in their installation manuals. This widespread manufacturer acceptance ensures installers can confidently specify UL 1738 vent pipe while remaining fully compliant with equipment warranties and code requirements.
In addition, leading industry organizations such as AHRI (Air-Conditioning, Heating, and Refrigeration Institute) and HARDI (Heating, Air-conditioning & Refrigeration Distributors International) actively support the adoption of polypropylene venting systems. Regulatory trends also reinforce this shift, with states like Massachusetts and New Hampshire, and provinces such as British Columbia, placing restrictions on PVC venting in favor of UL 1738 polypropylene vent pipe.
Together, manufacturer listings, industry group support, and evolving code requirements demonstrate that UL 1738 polypropylene vent pipe is a well-understood, trusted, and widely supported venting solution across the HVAC industry.
