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VII. Venting
E. Assembly of CPVC/PVC Vent Systems (continued)
WARNING
Asphyxiation Hazard. Failure to follow these instructions could cause products of
combustion to enter the building, resulting in severe property damage, personal injury or death.
•
Use all CPVC vent components for near-boiler vent piping before transitioning to Schedule 40 PVC pipe
(ASTM 2665) components for remainder of vent system.
•
Use CPVC vent components within any interior space where air cannot circulate freely, including through
vertical or horizontal chase ways, inside a stud wall, in closets and through wall penetrations.
•
The use of cellular core PVC (ASTM F891), cellular core CPVC or Radel (polyphenolsulfone is prohibited).
•
All condensate that forms in the vent must be able to drain back to the boiler.
•
Never leave the boiler in operation without the gas sample cap in place (Figure 7.27).
1. Assemble the vent system, starting at the boiler:
a. If 3" PVC is to be used for venting, a 3" CPVC elbow and the 30" straight section of CPVC must be used
before transitioning to PVC. If necessary the 30" straight section of CPVC may be cut at any location and a
CPVC elbow can be inserted between the two resulting segments.
b. When cutting CPVC or PVC pipe, use a miter saw or a saw designed to cut PVC pipe. Use a miter box or
other method to cut pipe squarely. De-burr both the inside and outside of the cut end.
c. Dry fit all vent components before assembly.
d. The vent adaptor has three different inside diameters. The larger (upper) inside diameter accepts 3" CPVC
pipe and is used in this application (the middle inside diameter accepts 3" nominal PolyPro, Polyflue or
InnoFlue, and the smaller, lower inside diameter accepts 3" stainless steel). A locking band clamp in the
adaptor prevents the vent pipe from coming out of the adaptor once it is installed and tightened. Lubricate
the gaskets in the vent adaptor with water and insert the first piece of 3" CPVC into the vent adaptor until it
bottoms out. Tighten locking band clamp to secure vent pipe.
e. If 2" CPVC is to be used for the vent system, reduce the first piece of 3" CPVC installed in Step (b) to 2" CPVC
using a CPVC reducing coupling or elbow. Otherwise assemble a 3" CPVC elbow and remainder of 30"
CPVC piping before transitioning to PVC. If 3" PVC is used, the first piece of PVC will either be connected to
the CPVC elbow or the end of a section of CPVC vent pipe. In the latter case, a PVC coupling may be used to
connect the first piece of PVC to the last piece of CPVC.
f. Clean all CPVC and PVC components with the appropriate primer before cementing. Cement the vent system
together, starting at the boiler and following the instructions provided on the cans of cement and primer. Use
a field supplied cement and primer that is listed for use with the materials being joined (CPVC and/or PVC).
The following, or its equivalent, may be used to join CPVC to PVC:
•
IPS Corporation #P-70 Primer
•
IPS Corporation #790 Multi-Purpose Solvent Cement
Always use primer on both the pipe and fitting before applying the cement. Assemble the pipe in accordance
with the instructions on the cans of primer and cement.
107672-03 - 5/18
E. Assembly of CPVC/PVC Vent Systems
43
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