Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

DIRT and AIR Separators - Recommendations?

hydronical Member Posts: 24
I am a newbie working on my hydronic system, with its 1991 Pennco (Dunkirk?) boiler. I need to replace an expansion tank, and while the system is drained, I'd like to add some reasonable upgrades. Right now, I have poorly placed Amtrol float air vents, but no air separator or dirt separator. Here is a photo of the system.

In a separate post, hot rod recommended a Caleffi 5461 Discal DirtMag, which is a combined air, dirt & magnetic separator. Seems like a great device, though it is a little pricey.

Does a combined air, dirt and magnetic separator work as well as single-purpose devices? How important is the magnetic feature? For my home heating system with 3/4" piping, what makes the most sense? I want a quality device, or devices, that will last for a long time.


  • hydronical
    hydronical Member Posts: 24
    Referring to the photo of my system, if I purchased an air separator and dirt separator as separate devices, would they be installed in different locations? Is this a good reason to buy separate devices?

    For its 5453 DirtMag dirt separator, Caleffi recommends that it be installed on the return circuit upstream of the boiler, and always upstream of the pump.

    For its 551 Discal air separator, Caleffi recommends that it be installed after the boiler and on the pump suction side.

    Interestingly, Caleffi recommends that the 5461 combined air, dirt & magnetic separator should be installed after the boiler and on the pump suction side. This seems to favor air removal over dirt removal.

    In my system, the circulator pump is attached directly to the boiler on the return side. I do not want to move the circulator pump or do any major repiping for this project.

  • Snowmelt
    Snowmelt Member Posts: 1,415
    Do what u want to do some thing better then nothing
  • hot_rod
    hot_rod Member Posts: 22,144
    Good observations, a dual purpose device like a Air/Dirt separator does present the question of where to best pipe it.

    Then best location for air removal is at the supply out of then boiler, the hottest fluid temperature. If you have a conventional cast boiler for example, placing the circ pump and expansion tank and fill valve at the separator is a common practice.

    With a modcon boiler, the manufacturer may recommend the circ pump is on the return, pumping into the boiler. This assures the boiler HX "sees' the additional delta P the circ supplies to the system. When pumping on the return, the expansion tank should be mounted at the suction side of the circ. I would still have the air separator on the hottest supply side for optium air removal.

    For dirt separation it is best to have that at the return to catch any particles before they get then pump, hx, zone valves etc. So with two separate devices you can get the best of both.

    With a dual purpose it's a toss up. I'm most concerned with air removal, with a combo unit on the supply side it will still grab dirt and debris, after a trip around the boiler of course.

    Mag separation gives ECM circulators an extra level of protection from any fine magnetic particles that would slip thru a strainer of dirt separator. I highly recommend them with permanent magnet ECM type circ pumps.

    It is a bit confusing deciding which product or products to use., Good air removal is a must on modern, high efficiency equipment, dirt removal is a good recommendation to protect the entire system. Once you go back and blow down the dirt from a separator, or remove then magnetic band and see what comes out of a system, you will be a believer.

    Connecting any new equipment to iron pipe systems or systems with cast-iron rads, I would always add dirt removal devices.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • hydronical
    hydronical Member Posts: 24
    Great information! Looks like my best bet is separate devices for better performance; and the price for separate devices is only slightly higher than that of the dual purpose device.

    What are the best air separators and dirt separators on the market for residential use?
  • SWEI
    SWEI Member Posts: 7,356
    If your system uses primary-secondary piping, a three- or four-in-one design (including hydraulic separation) can do it all.

    I like the Caleffi DirtMag a lot. Lots of options for MBR air seps.
  • RobG
    RobG Member Posts: 1,850
    Unless you are having problems I would not make changes to that old system until you are ready to replace it. If it aint broke, don't fix it.
  • BigRob
    BigRob Member Posts: 322
    The SEP4 is pulling a lot of iron oxide particles out of our system. We had a very bad leak a while back and are still recovering. I really think these kinds of products are very good insurance.