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Hoffman 70A

delcrossv Member Posts: 502
How does the 70A compare to the 40- faster, slower? (not listed in the guide to vents)
It's twice the price, so I'd like some guidance before I get some.
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.


  • Steamhead
    Steamhead Member Posts: 16,236
    Slightly slower. ISTR it's more expensive because it is built to military specs.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • dopey27177
    dopey27177 Member Posts: 887
    The difference between the #40 and 70a valve is the operating pressure.

    The 70a is good to 15 psi max and the 40 is good to to 10 psi max.

    In a normal operating system in lower pressure applications such as systems that operate at pressures under 5 psig I would certainly use the #40 vent valve. There is no difference in the air discharge rate that would be meaningful.