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dirt separator before or after return circulator

naphelge Member Posts: 9
edited July 2016 in Gas Heating
All my primary boiler parts arrived and I am just about to put them together. As I am laying them out to maximize space efficiency, it occurs to me that the layout would benefit if I install the dirt separator before the return circulator back to the boiler. It also seems that if the dirt separator were placed immediately before, that the return circulator would benefit from return water that has just had any dirt removed from it. But I wonder if there might be a logistics reason why a dirt separator should be installed after a return circulator, just as an air separator should be placed before the supply circulator?

In case it matters, here is a link to the dirt separator that will be installed:

Thanks in advance for opinions, suggestions and advice.


  • hot_rod
    hot_rod Member Posts: 18,222
    Separators work a bit different than strainers. The strainer captures the debris in the screen and reduces flow as it filters, so they need regular maintenance, certainly at startup. A plugged or partially plugged strainer presents quite a bit of pressure drop that you do not want at the circ inlet, as it can induce cavitation.

    In a perfect hydronic world, a gauge or gauges would be placed across the Y strainers to indicated needed service, like many pool filters use.

    A separator removes the particles and allows them to settle down to the lower portion and does not reduce flows. Unless they plug solid from excessive teflon tape application :) We also had a larger pipe size version one returned with a brown jersey glove stuck inside. Very low pressure drop through a separator.

    Separators will remove down to a 5 micron particle size after multiple passes.

    I think upstream of the circ would be the better location.
    If you are considering an ECM circulator now or in the future, a magnetic separator function is highly recommended.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • naphelge
    naphelge Member Posts: 9
    edited July 2016
    HotRod thanks for the quick reply and very helpful info.

    Just for the sake of clarity, when you say "upstream of the circ," on the return flow side that would indeed put the dirt separator before the circulator that is pulling water back to the boiler? So it would be:

    return water ===> closely spaced tee ===> dirt separator ===> circulator ===> boiler return

    I am glad I went dirt separator instead of y-strainer now. But had I asked my question earlier I would have been able to purchase the "magnetic separator" you suggest, even though the grundfos circulators (UPS15-58FC for both supply and return) do not employ ECM technology.
  • SWEI
    SWEI Member Posts: 7,356
    Most dirt separators by design have essentially zero head loss. We install them ahead of the circulator in order to help protect the motor & bearings from damage.