Guide to Polypropylene Venting

What is Polypropylene venting for and why do we need to know about it? 


Polypropylene venting is specifically designed to handle the conditions created by gas vented high efficiency appliances. Typical DWV Sch 40 PVC was never designed to be an appliance venting material. It has been used for venting because of its inexpensive cost. However, according to Charlotte Pipe Company Schedule 40 PVC is reduced to 22% of its original strength when PVC reaches 140 degrees. Most high efficiency furnaces flue will run under this temperature if they are running correct. The danger though is if there is a fault, PVC could fail. That is why there is now a UL-1738 safety standard that some states and municipalities are beginning to implement for all gas fired equipment. This standard gives a 70°F cushion on the venting material. This means that the failure temperature is 70°F above the rated temperature of the pipe.

The differences between Polypropylene venting and PVC


The rating of Centrotherm InnoFlue is 230°F. This means it is safe for all high efficiency equipment - both boilers and furnaces. It is something we highly recommend for any contractor installing a boiler where the return water temp is going to be higher than 140°F. If the design of the system is designed around a 20°F differential, that means the max temperature outlet would be 160°F. The reason for this is that if all the water is above 140°F, the flue temperature at the outlet of the boiler will be more than 140°F. This is above the rated safe temperature of typical PVC. There is some PVC that is rated at a higher temperature, but it is still only designed to a UL-1738 rating of 149°F. For all those systems that need 175°F water, polypropylene pipe is still recommended.

Centrotherm InnoFlue pipe is installed slightly different than PVC. It is a bell end pipe which means there are no couplings. Centrotherm needs at minimum a ¼” per foot of fall. The “90°” elbows are 87°.  Innoflue is a bell pipe which means it can be cut but the cut pieces are going to be unusable. The pipe comes in 1’, 2’, 3’, 6’, and 10’ lengths. It does take a little more thought than PVC, but it is like B-Vent lengths have been for years. The biggest difference in figuring out your lengths is that Centrotherm InnoFlue can be cut down.

Centrotherm pipe has some different options PVC doesn’t have. You can use a Concentric pipe if you desire which is a pipe within a pipe so you can run the intake and exhaust out in one. They also have a flex pipe that can be used in either an old B-vent as a liner or in an old brick chimney. The flex pipe can only be run on the vertical though and special supporting must be followed.

Quick tips for using Polypropylene venting 


The putting together of the fittings and pipe is very simple. It just means lubricating the pipe with the Centrotherm lubrication and pushing it together and pushing the safety connector on. Watch the linked 1-minute videos on how to install centrotherm pipes. Also see the quick guides to see what fittings and pipe are available.

InnoFlue Quick Guide 

Centrotherm InnoFlue Joint Connection Tutorial

Centrotherm InnoFlue Field Cutting + Deburring Tutorial

Centrotherm InnoFlue Elbow Rotation Tutorial

Contact the B-Y customer assurance team with any questions on centrotherm products and how to use them. 

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