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Do I even have main vents, let alone sufficient ones?

I've been doing some reading on this wall about the importance of having fast main vents. And while I do see a couple of vents near my boiler (the Vent Rite 33s pictured), I'm not sure whether these are what's being talked about when people talk about main vents, and was hoping someone might be able to help me get a better understanding on that. Those Vent Rites aren't on particularly large pipes, and I'm not really sure what the pipes they're on do — they disappear into a wall never to be seen again. I've also attached a second photo showing how the pipes the vents are connected to attach to the boiler down below.

The reason I even looked at the piping around the boiler is because the (adjustable) air vent on my bedroom radiator seems intent on hissing and whistling and waking me up. I was considering getting a new vent for that radiator to shut it up, but don't want to have the new one scream at me, too. So I wondered if it's whistling because there's too much pressure in the system, maybe because insufficient or non-existent main venting?

Any insight would be much appreciated.


  • gfrbrooklinegfrbrookline Member Posts: 369
    No, you have radiator vents on your mains that are also in the wrong place.

    How long and what diameter are your mains? Is this one pipe or two?
  • JUGHNEJUGHNE Member Posts: 5,648
    Too small for sure, they might be on the right pipe though.
    Can you back up for pictures showing those 2 pipes dropping and where/if they tie together going down to the boiler?
  • gfrbrooklinegfrbrookline Member Posts: 369
    Are you also thinking they are where the dry returns drop down to the the wet returns? If so they need to be set back 1" and on a nipple 6-10" above the return.
  • gilead1234gilead1234 Member Posts: 8
    Many thanks, everyone. @gfrbrookline , it's a one pipe system, and the diameter of the main (as calculated from the outer circumference) is 2.4" from outer edge to edge. When measuring the length of the main, do I measure the entirety of it's horizontal loop around the basement/garage, from where smaller pipes come out vertically up to the radiators? If so, it's roughly an 80' circuit.

    @JUGHNE , the two pipes do tie together on the way down to the boiler. I'll attach a hopefully better photo of that in a separate comment below.

  • gilead1234gilead1234 Member Posts: 8
    Here are pics of the two pipes tying together.
    3036 x 4048 - 3M
    3036 x 4048 - 3M
    4048 x 3036 - 3M
  • JUGHNEJUGHNE Member Posts: 5,648
    It looks like your steam main splits and goes in 2 directions.
    This would match the 2 "dry" return pipes you have.

    To improve the main vent issue, you can remove the reducer bushing where the little vents screw into. Then install a 3/4" nipple, 90 up, nipple, 90 pointing to the wall , long nipple, 90, and then up 6" or so to install a vent in the vertical position.
    This provides piping resistance to any water hammer that would wreck any new vents. I would try Barnes & Jones Big Mouth air vents for that location.

    But your 2 dry returns should each drop down below the boiler water level line. This will keep steam from the shorter return from prematurely closing the vent on the longer return.
    That will involve some pipe work.

    I would just go for the new air vents now and see how things work out. IIWM
  • gfrbrooklinegfrbrookline Member Posts: 369
    You want to measure from where it comes out of the boiler to where it goes up to the last radiator. Since you have two vents I am guessing you have two mains so measure both and tell us the length of each. Also tell us the length of the smaller pipe that leads back to the boiler since that is where your vents are located, these are called dry returns.
  • gilead1234gilead1234 Member Posts: 8
    Thanks @JUGHNE. I'm not the most adept at this kind of stuff. Is this what it's supposed to look like at the end of the process you describe (with the same setup also on the second dry return)?

    @gfrbrookline, the dry returns, and some of the main, disappear into the wall and above the bathroom ceiling. I can try to pop up the drop ceiling for a more precise measurement. Are the precise measurements needed to figure out the size of the main vents?
  • You can also put on a 0-3 psi gauge, and add big mouth main vents, until you see the air escaping at 2ounces.—NBC
  • JUGHNEJUGHNE Member Posts: 5,648
    Yes, you have the idea. The horizonal nipple you add should slope slightly to drain back to the first 90 ell. Head back parallel above the old pipe which has the slope you need.
    That bushing looks like 3/4" pipe thread.
    If you spray it numerous times over several days with PB Blaster or Kroil spray it may loosen up.

    Most here recommend the B&J Big Mouth air vents. Best buy for the money. You can not vent too much in your situation.
  • gilead1234gilead1234 Member Posts: 8
    edited November 2018
    @JUGHNE Should I use Y strainers, as some have talked about here, to protect the vents? If so, would you mind giving me an example of what size/material/etc Y strainer I might use? And how important is it to balance the two dry returns, i.e. to have different sized vents on each if the mains are different lengths? Would it mess things up to just put two Big Mouths, regardless of respective lengths?
  • Like this:

    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
  • Jamie HallJamie Hall Member Posts: 10,383

    @JUGHNE Should I use Y strainers, as some have talked about here, to protect the vents? If so, would you mind giving me an example of what size/material/etc Y strainer I might use? And how important is it to balance the two dry returns, i.e. to have different sized vents on each if the mains are different lengths? Would it mess things up to just put two Big Mouths, regardless of respective lengths?

    Proper piping as shown in @New England SteamWorks 's post, will protect the vents just fine. No need for strainers. It is helpful to balance the two mains, but unless they are really very different it's not necessary to be too fussy. Try two Big Mouths first, and go from there.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • gilead1234gilead1234 Member Posts: 8
    So, I have an update to the above (which doubles as a request for updated thoughts from the Wall, @New England SteamWorks , @JUGHNE et al):

    I had hoped to get New England SteamWorks to come look at my system, install a couple of big mouth's I bought (the bushing connecting those small main vents was stuck on there really good, so I couldn't do it myself) and to help me eliminate the wake-up whistle from my bedroom rad vent and a new clanking sound from another bedroom radiator. But those guys seem to be in very high demand and haven't been able to schedule a visit to my part of town.

    So I got another plumber/heat worker in here, who emphatically told me that my big mouths aren't actually vents, but traps. Since he's the plumber and I can't pretend to know much about heat, I didn't feel like I was in position to argue. He also suggested that the whistling and clanking was because the ventrite #1s on all my radiators weren't wide open.

    So, after splitting the bushing in half trying to remove them (told you they were stuck on there really good!) he eventually replaced the vents pictured above with Hoffman #1s -- at the same location where the current vents are, and not up and back, as suggested above. And he opened the adjustable Ventrites all the way all up on every radiator throughout the house.

    Again, it didn't feel like I was in a position to suggest otherwise. He's the plumber, I'm someone who's read an internet forum. He certainly knows more than me, and I don't doubt that there may be a reason for his decisions.

    But I do wonder what people's thoughts are. I've read again and again that the mains should be vented fast and the radiators vented slowly. Are Big Mouths main vents and not steam traps? (Do they just look like steam traps)? The #1s are, I assume substantially slower than Big Mouths. Are they fast enough? And is indeed there any reason it might be best to have the setting on the adjustable ventrites open all the way throughout the house? He suggested, if I remember correctly, that by turning them down I was creating too much pressure in there, particularly if my boiler is too big, which he speculated was possible. Maybe in my setup wide open is best?

    At any rate, the whistling hasn't gone away, and the clanking hasn't either. :neutral:

    Any thoughts? If everything is as it should be now, I'd certainly like to try to return those pricey big mouths.
  • FredFred Member Posts: 7,846
    The Big Mouth is a Trap that Barnes and Jones re-designed to be a Main Vent. It needs to go on your mains. Tell the plumber to stay up to date on changes in the market and to just put them on. They must be installed vertically. Now that he got the old ones off, you can put them on yourself.
  • gfrbrooklinegfrbrookline Member Posts: 369
    Do you mean a Gorton #1? If so way to small but at least you have the tapping for the the Big Mouth.

    To install the Big Mouth you will need a 5/8 allen wrench, teflon tape and a large adjustable wrench. Unscrew the Gorton, wrap the spud of the BM with the tape and screw it in with the allen wrench then secure the vent with the large wrench, make sure it is straight up and down. After you secure the vent to the spud run the boiler up heat to make sure it is properly mated and you are not blowing out steam.
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