Hi all,
Long time listener, first time caller.
Does any know of a code requirement for using oxygen barrier PEX in a hydronic heating system, particularly in a system modification situation? I searched through the 2018 IRC and 2018 IMC and I didn’t see any requirements for using it. I’m a bit surprised, since all of the documents I’ve read from manufacturers recommend using oxygen barrier PEX if there is ferrous metal in the system.
This thoughtfully designed home preserves the character of its neighborhood while maximizing space for a growing family through careful attention to scale, rooflines, and material choices.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
In simple terms, you want to use an oxygen barrier pex with a closed system. Hydronic heating systems are almost always closed. In other words, you fill the system with water and leave the same water in the pipes and boiler indefinitely.
Domestic hot water systems (showers, sinks, etc.) do not require the oxygen barrier style pex tubing.
I apologize for not answering your question. I am not aware of a code that requires the oxygen barrier (yet).
Chapter. 21 in the 2021 IRC deals with this. Table M2101.1 shows acceptable piping and fitting materials, including PEX and PEX-AL-PEX. The table lists two ASTMs that must be met for PEX - F876, which is basically dimension tolerances, and F3253, which is ... Standard Specification for Crosslinked Polyethylene (PEX) Tubing with Oxygen Barrier for Hot- and Cold-Water Hydronic Distribution Systems. For PEX-AL-PEX, which is a type of oxygen-barrier PEX, the ASTM is F1281.
If oxygen-barrier PEX were not required (though it is), you'd want to look at the manufacturer information for the other components of your heating system to see what they recommend/require. As was mentioned in a recent FHB Know the Code, following manufacturer instructions is generally required for a code-approved installation.
Thanks, Matt. I see that now in the the 2021 IRC. But it appears to have been added for 2021. The 2018 IRC, which is enforced by my municipality, does not include ASTM F3253 in the table; it only has F876.
My hydronic system has old 2in cast iron pipes. The 1/2in copper lines that branched off of them to a radiator were disconnected during a renovation, and are now being replaced with PEX. I was surprised to learn the plumber was not planning to use oxygen barrier PEX, but he had no problem with using it when I asked him to. I just wanted to check the code in case he resisted my request.