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Hissing Return Vents

rhwrhw Posts: 40Member
Wet return vents were hissing this morning for the first time. They were installed several years ago. Also it seems that the water level in the sight glass has gone down some although no obvious leaks and no white smoke coming out of the stack. Is this something that needs to be addressed immediately? I have attached some pictures and there are others from a previous post. All help greatly appreciated


  • neilcneilc Posts: 498Member
    What's your boiler pressure set to?
    What do you see on the gage at its highest?
    Post a picture of the boiler and the control and gage.
  • nicholas bonham-carternicholas bonham-carter Posts: 7,513Member
    edited November 24
    No doubt your pressure may have increased beyond the maximum set on the pressuretrol. This can be caused by the pigtail underneath becoming plugged. The cure is to remove the pressuretrol, and unscrew the pigtail, to give it a good wash out. Check the settings on the pressuretrol at this time as well, and set it as low as possible,-1.5 psi off, and 1 on.
    Getting a low pressure gauge, (1-3 psi) is so important for keeping these systems honest, that I don’t know why they are not supplied with each new boiler, along with the required 0-30 psi gauge.
    Unless your system is very very small, that main vent is too small to get the air out quickly. Perfect balance, with the steam arriving at each radiator simultaneously, needs the air to be let out with very low resistance.—NBC
  • rhwrhw Posts: 40Member
  • gennadygennady Posts: 709Member
    edited November 24
    If air vent fails open, escaping steam makes hissing noise. Steam gets lost and water level drops, if you have no automatic feeder, which refills boiler to maintain water level. Replace hissing air vent.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • neilcneilc Posts: 498Member
    Looks like you have room to dial the Ptrol down a bit and lower your pressure setting.
    Is that picture taken while the boiler is running?
    Is the pigtail clear.
    How does the water look in your sightglass? Dirty ?
  • rhwrhw Posts: 40Member
    yes. picture taken while boiler was running and have not removed pigtail to see if clear. also sight glass water does not look particularly dirty.
  • neilcneilc Posts: 498Member
    clean water is good,
    check that pigtail.
  • rhwrhw Posts: 40Member
    Will do. If I can figure out how to do. Is there a youtube or other video instruction guide somewhere? Thanks.
  • Jamie HallJamie Hall Posts: 8,945Member
    Ah... back up a moment. If this hissing vent is on a return (and not on an extension of the steam main), you may have a failed trap out there in the system somewhere. Check them all.

    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
  • rhwrhw Posts: 40Member
    I now think the hissing of the vents on the returns "may" have occurred due to a Thanksgiving guest who boosted the thermostat by 5 degrees to try and warm up the house fast since it has not happened since that time. However it appears that I am still adding water to the boiler once every two weeks. Not sure how much but the boiler shuts down and a red light goes on. Any thoughts on a fix?
  • Jamie HallJamie Hall Posts: 8,945Member
    Probably right. Nothing like folks tampering with thermostats.. (ask me about a church I care for someday).

    How much water are you adding? A gallon or so every two weeks isn't that bad. Be nice if it were less, but so long as it is consistent... and finding out where it's going could be a real bear. That small a loss just isn't going to show up real well.

    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
  • JUGHNEJUGHNE Posts: 4,942Member
    Jamie, churches and thermostats...I know off topic but:
    I put 2 Visonpro's in a church mainly because of the locking feature. The screen is locked on setting "1". They can raise or lower temp until the next time programed. I have to go there twice a year to change from heat to cool and back.
    The church leaders asked to a meeting to explain how to operate the T-stat. The deer in headlights were all gathered around the table.
    They said they wanted to know about it as I would not be around forever...….I was the youngest person in the room.
  • BobCBobC Posts: 4,861Member
    @Jamie Hall I was working at a factory when the first energy crunch hit, the owner was outraged at the cost of heating the plant and wanted to lower costs

    He knew I had just installed a new setback thermometer and asked it could be done for the plant. I warned him about all the mass that would have to be brought up to temperature but he wanted it done. I requisitioned the thermostat and set the thing up but I mounted it on a partition so it was out of sight so the workers could diddle the now disconnected thermostat to their hearts delight.

    The boss initially wanted the heat to come back up at 7AM but that left the plant frigid when people started working at 8AM. I walked it back to 5AM which meant things had come most of the way back by the time folks clocked on.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • rhwrhw Posts: 40Member
    Looks like water is below the LWCO and shutting down the boiler in a weeks time. Where is it going? Again I see no leaks or white smoke.
  • FredFred Posts: 6,960Member
    Do you have any returns buried under the basement floor? That much water has to be going somewhere. Does the basement or any other rooms in the house seem unusually humid? That may be a clue to a faulty vent. Is this a one pipe or two pipe system?
    Have you cleaned the pigtail yet and reduced the setting on the Pressuretrol?
  • nicholas bonham-carternicholas bonham-carter Posts: 7,513Member
    Maybe it’s time to do the overfill test to discount a leak in the boiler itself.
    Turn the boiler off at the switch.
    Wait an hour or so to cool down to warm from hot.
    Fill with fresh water, until you can feel cold water in the header above the boiler.
    Wait a couple of hours or more, and check for water on the floor, or in the firebox.
    Don’t forget to drain down the boiler to the recommended level before turning it back on.
    Post the results here when you have completed this test.
    Is this system one pipe, or two?—NBC
  • rhwrhw Posts: 40Member
    One pipe system and all piping is visible. No additional humidity in the house. Although I do a lot of diy stuff removing the pigtail for some reason seems a little daunting. Should it be? I will also knock the pressuretrol down a notch.

    As far as turning off the boiler I guess I should wait for a little warmer weather as I may get thrown out of the house. Right now our highs are in the upper 30's.

    Thanks for all your help but I'm still confused as to why I would lose all that water and not see a sign of it anywhere.
  • neilcneilc Posts: 498Member
    take the time and do NBC's test,
    that water might be going up the chimney.
    Send wife and kids to the movies.
  • FredFred Posts: 6,960Member
    @rhw, taking the pigtail off and cleaning it is a simple task. Shouldn't take more than 15 minutes barring any surprises (which I know is what you are apprehensive about)
  • rhwrhw Posts: 40Member
    Took off the pigtail and cleaned it out. Getting it cleaned took much longer than expected. Probably did not have the right stuff to unclog it with. Fingers crossed that this is the fix. Thanks to everyone.
  • ethicalpaulethicalpaul Posts: 185Member
    Was it clogged to the point of resisting air flow through it? If so, good work!
  • neilcneilc Posts: 498Member
    yeah, let us know either way if symptoms persist
  • rhwrhw Posts: 40Member
    It was so clogged that it resisted air flow. It took a while to clean out.
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