FAQs

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.

InnoFlue® is approved for gas-fired Category II and IV appliances and is suitable for vertical or horizontal venting in new or retrofit installations, including chimneys, chases, and through-wall terminations. InnoFlue® Poloprophyline also meets UL-1738 code.

Connector Rings are required for an installation of 2″ through 5″ diameter InnoFlue® to be UL-1738 and ULC-S636 compliant. Centrotherm strongly recommends the use of Connector Rings on all installations. Diameters 6″ and larger do not require the use of Connector Rings.

InnoFlue® Polypropylene Special Gas Vent Systems can be field cut to length using a hacksaw and miter box or equivalent. InnoFlue® must be cut on the male end of the pipe, preserving the socketed (female) end. After making a cut, the end can be beveled at the contractor’s discretion. The end must be deburred using a standard deburring tool or sand paper.

Yes, the exterior of InnoFlue® can be painted. Please follow the surface preparation specified by the paint manufacturer.

Yes. For rooftop terminations, follow flashing and sealing instructions. Vertical terminations over 59” above the roof line must be supported with guy wires or braces.
 

Not directly. For underground applications, InnoFlue® must be installed inside a larger diameter, direct-bury-rated pipe. The vent must be pitched, supported, and allowed to expand/contract inside the sleeve.

Yes, InnoFlue® Flex can be field cut, but only in the rigid sections and when connecting to the female end of Single Wall.

When venting combustion gas, InnoFlue® Flex cannot be installed horizontally. The installation of InnoFlue® Flex in a horizontal configuration allows for the pooling of condensate. This can create sagging in the vent system leading to the creation of back pressure. Back pressure can result in a forced shut down of the heating appliance.

InnoFlue® Flex and BlitzFlex® can be installed horizontally when used as an air intake.

InnoFlue® Flex can be installed in a shared chimney, assuming the flues are separated, if the ambient air temperature does not exceed 300°F (149°C).

InnoFlue® Flex should not be installed in a sheet rock wall.

InnoFlue® Polypropylene Special Gas Vent Systems can be installed in chases with offsets that do not exceed 45°. Chases can have multiple offsets.

No, InnoFlue® Flex is UL-1738 and ULC-S636 listed exclusively for use as a combustion gas vent system inside of a chase.

The InnoFlue® Concentric vent kit must always be installed according to Centrotherm’s official installation instructions to ensure safety, compliance, and system performance.

The concentric vent system can be installed in a variety of chases, including masonry, B-vent, and sheet  rock chases, offering flexibility for different construction types.

InnoFlue® Concentric vent kit combines exhaust gas venting and combustion air intake into a single concentric vent system. This design allows for a cleaner, more aesthetically pleasing installation, reduces the number of roof or wall penetrations, and helps save on labor and installation time..

A concentric vent is a type of venting system that incorporates both exhaust and intake air in one pipe-within-a-pipe design. The InnoFlue® Concentric vent kit features a durable metal outer with a polypropylene inner. Combustion gas is drawn through the space between the two pipes, while exhaust gases are safely expelled through the polypropylene inner pipe.

The InnoFlue® Concentric vent system is engineered to withstand flue gas temperatures up to 230°F (110°C).

InnoFlue® Concentric vent kits are approved for use with gas-fired Category II and Category IV appliances, making them versatile for residential and commercial applications.

InnoFlue® Lite is a lightweight, CE EN 14471-certified polypropylene venting system designed for use with Category II and IV gas-fired appliances (U.S.) and Class II C appliances (Canada). It is suitable for residential, commercial, and industrial applications with flue gas temperatures up to 230°F (110°C) and maximum pressures of 0.725 psi (5000 Pa).

Yes. Use paints approved for polypropylene, such as Rust-Oleum or Krylon. Remove ink markings with acetone, apply an appropriate adhesion promoter, and reattach the product label once dry.

Use Centrotherm-supplied support brackets when possible. Horizontal runs must be supported every 39" (1 m); vertical runs must be supported every 78" (2 m). Directional changes (elbows/tees) should be supported within 12".

Yes, InnoFlue® Lite is the perfect solution for air intake in both code and non-code markets.

Yes. All diameters of InnoFlue® Lite SW Rigid components are UV stabilized and suitable for exterior installation. Optional black components are available in 2" and 3" for aesthetic preference or enhanced performance.
 

Not directly. For underground applications, InnoFlue® Lite must be installed inside a larger diameter, direct-bury-rated pipe. The vent must be pitched, supported, and allowed to expand/contract inside the sleeve.
 

What does PP stand for in piping?

PP pipe stands for polypropylene pipe. It is a versatile plastic polymer used in many industries because of its durability and eco-friendly profile. In venting systems, PP pipe provides a dependable alternative to traditional materials, reducing installation time and improving system safety.

What is PP material made of?

PP, or polypropylene, is a thermoplastic polymer known for being lightweight, strong, and recyclable. Centrotherm uses flame-retardant polypropylene to manufacture InnoFlue® vent pipes and fittings, ensuring safety and durability in heating systems. This material resists corrosion and harsh flue gases, making it ideal for modern condensing appliances.

What is PP pipe?

PP pipe refers to piping made from polypropylene (PP), a durable plastic widely used in flue gas venting systems. Centrotherm’s InnoFlue® PP pipes are lightweight, gasketed, and engineered for safe, reliable venting. Unlike PVC, PP pipes don’t require glue or solvents, making installation cleaner, faster, and more environmentally friendly.

Learn more about our InnoFlue® Polypropylene vent systems.

BIMobject is the leading global platform for digital building products. Through our partnership with BIMobject, Centrotherm provides architects, engineers, and contractors with accurate BIM files and Revit files that integrate seamlessly into any Revit content library. This collaboration ensures you have access to the latest, most precise digital models of commercial Centrotherm systems for use in your BIM projects.

Yes. Centrotherm’s Revit files are available as Revit downloads directly through BIMobject. You can browse our full Revit content library and download the BIM files here.

Our vision of sustainability is encapsulated in our aim to evolve into a circular brand. This means that in all aspects of our operations, we look at how we can integrate sustainability and circularity principles. It's a continuous process of analyzing, adjusting, learning, and improving, in which we strive to be transparent about what we do and what we achieve. Together with our stakeholders, we evaluate the impact our company has and identify areas for improvement.

We've deliberately chosen not to prioritize specific sustainability initiatives. Instead, we've woven sustainability throughout our entire business operations, connecting it with distinct business strategies. For example, our sustainability principles in HR are integrated into the HR strategy. And our principles in the area of safety and health are included in our group Health & Safety strategy and rolled out from there. This approach enables us to actively address multiple themes simultaneously and make continual progress. This fits into our vision: sustainability is not a standalone theme. It encompasses all our business processes and is therefore an integral theme.

This is a crucial part of our sustainability pillar 'Our Solutions'. In our product design process, it's really important to think about sustainability and circularity and make smart choices. We have a clear product design process. From the beginning, when we set the product specifications, we ask questions about sustainability and circularity. For example, can we use recycled material? Where do we get components we don't make ourselves, and do those suppliers meet our criteria? In 2024, we're also going to start using Life Cycle Assessments in our product design process. This means that in the design phase, we look at the environmental impact of our new products. If we find ways to reduce that impact, we can do it before the product is made, rather than after.

In 2023, we started with a baseline measurement, using 2022 as our reference year. Every year, we gather new data and compare it to our reference year. In the meantime, we set targets on relevant KPIs, so that we can also communicate our progress each year.