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Main Venting

mdangelo Member Posts: 10
Now that I've learned (thanks everyone!) that I would be best served by swapping my Legend main vents with proper vents, I'm trying to figure out if it makes sense to have a pro come in and move them back at least 15 inches from the elbow as they presently are in the picture below. I presume they would function where they are and I also presume that the main vents have been in that particular location for over a hundred years and am hesitant to change it up but I also figure just because it's there doesn't mean it can't be improved upon. Thanks again to all the knowledgeable folks on the forum.


    JUGHNE Member Posts: 11,021
    I would just nipple up to a 90 ell, add a horizontal length of pipe, 90 ell up with maybe a 6 to 8" riser and put the venting on the top of that.
    The intent is to keep the vent away from any water hammer that may occur at the existing return 90 when it drops down to the wet return. Adding the lengths and 90 would help prevent any water slug from hitting the vent. Just so the vent can drain back down into the large pipe. Slope your new horizontal pipe back away from the large 90, the return is sloped to the large 90. The fittings would repeat that slope with your new pipe. The larger size is preferred, maybe 3/4".
  • Double D
    Double D Member Posts: 442
    edited April 2016
    You might want to start with just getting your mains vented. Increasing the venting on the dry return will do nothing for your rads that are one pipe and you may be freeing the path for the steam to jump over to the return side on your 2 pipe rads. I worked on a 2 pipe air vent system recently. All of the rads were 2 pipe with air vents and the dry return had vents on the drops to the boiler. It had no vents on the mains. After adequately venting the mains, all rads got their steam at the same time but the steam then took its next path of least resistance which was the return line. In the end , I removed the dry return vents, the system works fine. Even heating in all 3 apartments and no more hammering.

    It will be interesting to hear what you will need to do in the end.
  • mdangelo
    mdangelo Member Posts: 10
    I know my main problem is I'm not a plumber and every single plumber I've had over to the house refuses to work on the system because it's a steam system. We do have one steam plumber in town but I haven't had much luck with him. Number one, I don't want to make it work worse. Thanks for the advice!
  • Double D
    Double D Member Posts: 442
    Two pipe air vent system. Page 228 in Lost Art.