What is the difference between the PVC piping used in high efficiency furnace flues and that used for plumbing? Would it be o.k. to replace a faulty 2″ PVC furnace flue in a 92 AFUE sealed combustion furnace (Rudd achiever) with 2″ schedule 40 PVC designated for plumbing? The ASTM ratings are different, but I don’t know what that means. Thanks.
There are different PVC pipes designed for different types of applications. But in general it is the same PVC pipe used in plumbing and HVAC. With the condensing type furnace exhaust gases temperature being usually under 130F, PVC pipe temp rating around 150F is sufficient.
However, as always in such situations, you should follow manufacturer requirements for your furnace or local if it supersedes the above (some might require CPVC with 200F+rating).
The following are general requirements – Vent system and combustion air supply components of the high efficiency furnace must be constructed of schedule 40 PVC, PVC-DWV, SDR26, SDR 21 or ABS plastic pipe, fittings, sealants, and installation procedures that conform to the following ANSI/ASTM standards:
- PVC ASTM D-1785
- SDR26, SDR21 ASTM D-2241
- PVC-DWV ASTM D-2665
- PVC-DWV Cellular Core ASTM F-891
- PVC Primer And Solvent Cement ASTM D-2564
- ABS Pipe And Fittings ASTM D-2235
- Procedure For Cementing Joints ASTM D-2855