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Header and boiler riser size

I am going to be installing a new Peerless 63-04L boiler, and I have a question about the size of the header and boiler risers.  I am considering either two 2 inch risers with a 2 1/2 inch header, or two 2 1/2 inch risers with a 3 inch header.  Is there an advantage to using the larger size when my steam main is 2 1/2 inches?


  • Steamhead
    Steamhead Member Posts: 16,832
    The larger size

    will slow down the steam and do a better job of separating out any water that gets that far. The specified header is 2-1/2", but it can't hurt to go with 3". That's what I'd do if it were mine.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • CherylR
    CherylR Member Posts: 2

    Okay, thanks!  I will go with the larger size.
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    Header and Risers

    From what I've seen, the pros usually make the header at least 1" pipe size larger than the risers. I think this is because they want the cross-sectional area of the header to be as big as that of the two risers combined.

    NPS cross section

    2" 3.356

    2 1/2" 4.788

    3" 7.393

    3 1/2" 9.887
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,202
    I'm with Steamhead

    I'd go with the larger size too. 

    While the improvement between the two may sometimes be nearly immeasurable,  on some systems it will make a large difference.   By dividing the added cost, which is generally only in materials, over the years of the boiler's life, it's negligible.  

    I think the larger header is probably a good investment if you can do it.
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