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Double Pump

Hi, I looked at a hydronic system the other day that had a circulating pump on the supply side and another on the return side of the boiler piping. As the boiler fired and the pumps ran one could hear the distinct sound of air being pumped through the piping. I have never seen such a double pump set-up. Comments please? Btw, it's a cast iron boiler in a single family home; the radiators were originally gravity fed but were converted to a circulating system some years ago. Thanks!


  • HDE_2
    HDE_2 Member Posts: 140
    Series pumping

    Second pump in series offers same flow rate, double the head.

    The first circ was sized wrong or came with the boiler and when it didnt work a second was added??
  • InspectorDan
    InspectorDan Member Posts: 3
    Photo of Pumps and Piping

    I should have posted this in the first place. Sorry. 
  • InspectorDan
    InspectorDan Member Posts: 3
    Negative Ramifications

    Well.....what I'd like to know is. What are the drawbacks to having a pump on the return side of the boiler and another on the supply side. When the unit ran we could hear a lot of air going through the pump/s. Does this set-up make it harder to remove air from they system? Does it create turbulence or flow reduction? Thanks.
  • Joe Mattiello
    Joe Mattiello Member Posts: 703
    series pump, gravity system

    two pumps in series in an old gravity system!!  The water must be racing through the piping cauing velocity noises that could sound like air noises.  
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
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