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Must I use copper?

josephnyjosephny Member Posts: 53

I suspect this is a very (very) basic question, but I'm a complete newbie.

Must we use any copper in a closed radiant system?

Why not pipe exclusively in pex (3/4" or 1") from the boiler through the controls/pumps/valves/manifold/etc.?



  • PC7060PC7060 Member Posts: 193
    edited January 11
    Pex is commonly used in hydronic systems; it MUST have integrated oxygen barrier. For example, Pex-Al-Pex.   There are others as well. 
  • ZmanZman Member Posts: 6,341
    Any pex with an O2 barrier is acceptable and widely used.
    Many still prefer copper for the near boiler piping. It is easier to support and looks more professional. It can also handle the hot temps sometimes seen near the boiler better than pex will.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • josephnyjosephny Member Posts: 53

    Thanks guys!

    So, as long as I'm using hePex (for example), and not physically/mechanically supporting the components with the piping, and don't object to the aethestics of it, it's totally fine using 100% pex?
  • ZmanZman Member Posts: 6,341
    I sure don't know of a reason you cannot. What type of boiler is it? What temp are you planning on running. You should be aware that the inside diameter of the pex is quite a bit smaller than copper. You may have to upsize it to get proper flows.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Solid_Fuel_ManSolid_Fuel_Man Member Posts: 2,248
    Keep in mind that pex will expand/grow when its heated. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • pecmsgpecmsg Member Posts: 1,729
    If you want it neat and clean then all piping near the heater needs to be copper. The supply's and returns are then pex
  • Paul PolletsPaul Pollets Member Posts: 3,360
    The reason copper is used at the boiler is because of the higher temperatures developed within 5 ft. of the appliance. It's fine to connect pex after 5-6 ft. (barrier pex)
  • mattmia2mattmia2 Member Posts: 2,373
    Also clearance to the vent of conventional appliances and cost of the fittings to make a manifold and getting things heading in the right direction near the boiler.
  • josephnyjosephny Member Posts: 53
    Thank you all so very much! I'm learning so much, so quickly from all you very generous and experienced people.
  • EdTheHeaterManEdTheHeaterMan Member Posts: 1,636
    edited January 12
    I have suggested this to others with similar ideas. If you don't like to solder, rent a ProPress tool. If none are available for rent then go to eBay or craigslist and get a used one. After the project is done, then sell it on craigslist or eBay. Pro press fittings cost a little more but with good planning, you can use a combination of black iron and copper to support your attachments like; air separator, circulator, expansion tank, zone valves, and the like.

    Once you are far enough away from the boiler, and can neatly attach the PEX to a manifold, or support it on a wall or framing, then you will have a good working system that looks good too.

    After you are unable to work on it yourself, some professionals will need to make repairs and if you are not around to assist/instruct the guy, your loved ones will not be happy with the recommendations of the Pro.

    If I walked into something like this I would recommend an expensive repipe or a complete new system.

    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    Specialized in Oil Heat and Hydronics where the competition did Gas Warm Air

    If you make an expensive repair and the same problem happens, What will you check next?
  • JUGHNEJUGHNE Member Posts: 7,914
    If the boiler allows it, I use a lot of black pipe fittings and nipples.
    I use threaded components and a lot of unions.
    Black fittings and especially unions are less than copper fittings.
  • hot_rodhot_rod Member Posts: 14,425
    With larger bore pex, 1-1/4" for example the fittings get expensive and the crimp tool is quite large. Look at the flow rates 1-1/4 pex may be needed to substitute for 1" copper.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • josephnyjosephny Member Posts: 53
    EdtheHeaterMan: I went with a manual press (2, actually: Hydraulic on Amazon for $100 and manual on Supplyhouse for $180). Interestingly, both only go up to 1" copper and my new system needs 1-1/4" piping, so I'll be sweating some fittings (but not many). That's a great point about neatness -- saves immeasurable amounts of time later. Thank you!

    hot_rod: I looked around and noticed that the Uponor EP manifold uses 1-1/4" connections while the Uponor Stainless manifold uses 1", so I asked my supplier (who is also designing my system). He explained that the heating capacity (BTU carrying capability?) is around twice the amount for the 1-1/4" pipe and because I have plans to add zones later, he recommends staying with the 1-1/4" and sweating the handful of connections. Thank you!
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