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Main Vent Replacement Frequency

I have replaced my main vent once a heating season over the past 4 years. To me, that seems excessive. What's normal?


  • BobC
    BobC Member Posts: 5,473
    Should last many years

    A good main vent should last many years, if yours are plugging up with dsdiment you have a water quality issue. Sometimes you can clean out the sediment by boiling the vent in white vinegar for 10-15 minutes or just soaking it in some CLR.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Rod
    Rod Posts: 2,067
    Main Vent

    Hi- Yes,it sounds excessive. You didn't mention the make of the vent.Some vents are far better made than others. Also it may be that, due to your piping configuration, your vent is exposed to damage by water. hammer. If so you might want to put it on an antler. If the vents are clogged up, soaking them in CLR or boiling it in white vinegar sometimes frees them up.

    - Rod
  • Jettster
    Jettster Member Posts: 20

    I think it is being exposed to water and corroding the inside, the antler idea is a winner and I'll put it on this weekend! Thanks! I'll also soak the old one in CLR, see if that works. Thanks!!
  • Rod
    Rod Posts: 2,067
    Positioning the Antler

    Hi- Orient the antler so the water traveling down the main has to do a 180 degree turn to get into the antler.. Water doesn't like to turn corners so this will slow it down a bit. Also since the main is sloped, positioned this way the antler will be sloped so that any water reaching the vent will immediately drain away.

    - Rod
  • rmoore007ri
    rmoore007ri Member Posts: 45
    CLR ??

    um, what is CLR ??? Everybody else seems to know :-(
  • MDNLansing
    MDNLansing Member Posts: 297

    It stand for Calcium, Lime and Rust remover. CLR is the brand name of the product. Comes in small grey plastic jugs and can be found at any big box hardware store.
  • Jettster
    Jettster Member Posts: 20

    So, I put the antler on the main vent. Everything has been working great over the past month. Just now, 10:30pm on possibly one of the coldest nights, the main vent seems like it's going up again. CRAZY! It's kicking out tons of steam, causing me to have to refill my boiler twice in the past 2 days.
  • Jettster
    Jettster Member Posts: 20

    And I'm using the Hoffman #75. Is there a better one out there?
  • Steamhead
    Steamhead Member Posts: 16,732

    how long is your steam main? What pipe size? Is it the only steam main in the house?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Jettster
    Jettster Member Posts: 20

    Thanks for the quick response Steamhead! It's a one pipe system and I believe the steam main is 4" diameter. The distance from the boiler to the vent is around 35-40lf and it is the only steam main in the house. I was going to give you a buzz tomorrow if I can't figure it out tonight as I am also in Baltimore.

    I removed the vent, soaked it for a bit in some CLR and the valve seems to be seating properly now. I put on a 6" antler a few months ago. I guess it's a possibility it was stuck in the open position.

    When we moved into our home 7 years ago, I replaced all the bleeder valves on the radiators throughout the entire house. A couple now seem to be venting constantly. I guess they're due for replacement as well?

    Thanks again for your help! We're planning on moving in the Spring and renting out our house. We want to make sure the system is solid for potential renters come next winter. I'll definitely be calling to get it up to snuff!
  • JStar
    JStar Member Posts: 2,752

    What pressure are you making in the boiler? Anything close to 2psi will damage all of the vents in the system.
  • Jettster
    Jettster Member Posts: 20

    When the system is pressurized, the gauge above the low-fill cutoff says 5. I'll figure our how to dial it back a little.
  • Jamie Hall
    Jamie Hall Member Posts: 22,941
    The gauge says 5?

    Eek.  What does it say when the system is off and cold?  If the gauge is even remotely correct, you are way over pressure -- and that could very well be killing your vents.

    You probably have a pressuretrol -- what is it set at?  If you actually get Steamhead to come over, he may be able to help you with this.

    In answer to your principal question -- there are two main vents on the place I care for, set up on an antler.  One of them, a Hoffman 76, has been there working just fine since 1930; the other one, a Gorton #2, I added about ten years ago.  There is no real reason why a vent on either a steam main or a dry return shouldn't go on for decades, unless it is abused.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Jettster
    Jettster Member Posts: 20

    Oddly enough, I've kept the vents that stopped working. The one I replaced a few months ago, I soaked in some CLR and I think that may have fixed the issue. I'm holding onto that one as a backup, just in case. The one that went up last year, sounded like it had some debris in the bell. I shook the debris out into my hand, and it was rusted and corroded metal. I think the issue I had was not having the vent on an antler and the return water was getting blown into the bell. Probably from having the pressure set too high.