Download the revised IPEX 636 Installation Guide - Here (http://www.hvactechgroup.com/files/IPEX%20636%20Installation%20Guide.pdf)
Download this document to see the changes listed in pink - Here (http://www.hvactechgroup.com/files/IPEX%20636%20Changes.pdf)
QuoteStrapping shall be fixed to supporting structure (e.g. floor joists or cross members) using typical framing nails or screws. DO NOT USE sheet metal duct work to support System 636 piping.
The IPEX manual has been revised again, on March 20, 2017, and has removed the words "DO NOT USE sheet metal duct work to support System 636 piping." from Section 5.
You can download the revised IPEX manual - Here (http://www.hvactechgroup.com/files/System%20636%20Installation%20Methods%20Eng%2003202017.pdf)
Phew! They probably revised it after they found out how frequently it's impossible to strap without using the ductwork.
What's Royal pipe installation instructions say, maybe I'll just use their pipe instead.
Royal never had a requirement that said the venting cannot be secured to ductwork. This is exactly what I told IPEX, so they revised their manual. I was suprised and impressed IPEX did this so quickly.
I prefer to use IPEX because most of the rental water heater terminations, we are supplied with, are IPEX.