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Main Vent Replacement Recommendations

JH3550 Member Posts: 15
I just moved into a 1924 house with a single pipe steam system, oil fired. I read "We Got Steam Heat" and have been reading this site, which are all amazingly informative. It seems like I should replace the main vents on my system.

There are two main lines that run around the basement. At the end of each is a single Hoffman #4 vent. I have no idea how old they are. Pictures attached. Looking at the Balancing Steam Systems chart, they seem to vent way too slowly. They are also mounted on the elbow, which I have read is a bad place for them.

What would folks recommend I replace them with? Can I get away with installing a new vent in the same spot on the elbow?

Here are the main pipe lengths. They run around the perimeter of the basement, which is basically square:
East main: approx 48 ft in 3 sections
North Main: approx 31 ft in 2 sections



  • Chris_108
    Chris_108 Member Posts: 22
    I had a similar situation where an elbow was tapped and a vent put there but it never really worked right as the tap was too small probably 1/8th NPT. We ended up capping that and adding a vent further down towards the end of the run. YOU have to look at your piping to see if that can be done and how involved it is. My house was built in 1927 and also is a single pipe gravity steam system. I have two mains the hug the perimeter of each side of my basement. I have a big mouth and a Gortons # 1 on each side for a total of 4 main vents and system heats up considerably faster then it did prior. I am thinking about adding another vent to each side but not sure if that would be overkill. I would definitely replace those vents and try to put in better places. Is that only duct tape around the piping or is there insulation under all that tape? If the former you should really remove and get some decent fiberglass insulation around those steam mains! Oh what a labor of love it is having steam in these older homes.....

  • AdmiralYoda
    AdmiralYoda Member Posts: 629
    I have a similar piping arrangement as you. I have two Barnes and Jones Big Mouths at the end of each main. I started with one each on each main and that gave me a 90% improvement. I probably could have skipped adding the extra on each main but it does seem to help a little bit.

    I also have a gorton #2 at the end of a long riser as well. This helps steam get to that upstairs radiator a bit quicker. In general, you can't have too much main venting. You may waste a few dollars venting too much but I'd rather have a little extra than too little.