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.

Hoffman vent

mlandes Member Posts: 1
edited November 2020 in Strictly Steam
We recently had our yearly service done on our Lennox BSB-7D , model GSB8-225E. The boiler is 5 years old and is working properly; however, I was told that I needed one of my Hoffman 401434 vents replaced and it would cost $ for the part and labor. Two questions: First, I was told that it needed to be replaced because it had steam coming out of it because it meant that air could get inside of the system (is this true?). Second, is this something that I can just do myself? I am handy; however, I tend to stay away from HVAC.


  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    That's usually referred to as the Hoffman 75. It's a main steam vent. Your best bet is Supplyhouse.com. It's an easy job to remove it and replace it.

    The person who told you it needed to be replaced because steam was coming out... hmm. Is it? The vent is intended to stay open and let air out of the main until steam (or water) hits it, then close. If steam really is coming out, it probably does need replacement -- though they are pretty reliable (I know of some that have been operating since the 1930s without trouble). On the other hand, if air is coming out as the system comes up, it's just doing what it's supposed to do.

    And yes, when the system cools down, it will let air back in. It's supposed to do that to.

    Your tech. either doesn't understand what vents are for -- or needs a high profit job.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fred
    Fred Member Posts: 8,542
    That is a Hoffman #75. Go to SupplyHouse .com to buy a replacement, if you need one. They are less than 20% of the price you were quoted and take about 15 minutes to replace, if you have good access.
    You can take the one you have off and try to wash it out with vigegar. That may fix it. If it is leaking steam, it just means that the vent isn't closing all the way when steam hits it. All steam vents open, when cooled and let air into the system. You want the vent to close properly when steam hits it to prevent steam/condensate loss. Either try to clean it or replace it.
  • If the vent is not closing, then maybe the pressure is too high, and above 2 psi.
    A low pressure gauge, (0-3 psi), will show you what is happening.--NBC