Toilet "sucking" water from tub trap?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Houseman, Jan 27, 2013.

  1. Houseman

    Houseman New Member

    Joined:
    Jan 27, 2013
    Location:
    New Brunswick
    I have what I think is a weird problem. When I flush my toilet, there is a gurgling sound in my bath tub. When I run some water in the tub,and then flush, the noise stops, for a bit, (3/4 flushes) and starts again. Even more weird. this only happens on an intermittent basis. Sometimes it will go weeks without happening, then do it for a week. It seems that for some reason the toilet is sucking the water from the trap for the bath. I thought it might have something to do with the snow on the roof covering the vent stack but I just checked it from the ground) and it is open. Could there be a plug of snow inside the stack pipe that I can't see from the ground? (stack should be warm enough to prevent that?)

    Any thoughts/ideas would be most welcome. This is very annoying!

    Thanks!

    Trev
     
  2. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    That is normally because the tub is not vented, and the toilet siphons the p-trap.
     
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  4. Houseman

    Houseman New Member

    Joined:
    Jan 27, 2013
    Location:
    New Brunswick
    Would that cause an intermittent problem Terry? I have been reading here for an hour and came across threads that talk about dry traps(this one is used daily). I am kind of concerned now because I also read about "partial" clogging of the lines.
     
  5. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    If it is siphoning, it is because the toilet is flushing "good", so it would not be a stoppage problem. But, it could also be caused by air being forced out of the tub drain because of a stoppage. Your problem could be caused by NO vent, an IMPROPER vent, or a PLUGGED vent. The vent COULD be plugged with frost and you would not be able to see it without looking INTO it.
     
  6. Houseman

    Houseman New Member

    Joined:
    Jan 27, 2013
    Location:
    New Brunswick
    Thanks guys. I would tend to think that it is flushing "good". Nothing has changed in years so its not "no"vent or "improper" vent. Perhaps frost plug. I guess as long as it flushes well all is good.
    Thanks for your time both of you. I do appreciate it!
    ;)
     
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    FWIW, a toilet will often flush well without any vent...it's just the other things on the line that may have problems.
     
  8. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    quote; a toilet will often flush well without any vent

    FWIW, almost EVERYTHING will drain better without a vent. The vent is to keep it from draining so good that it siphons the water out of the trap. I once had a customer who wanted me to connect his tub drain to the stack. He had a 10' pipe dropping out of the tub all the way to the basement where he wanted me to make the connection. I told him that if I made that connection, the tub would drain so "good" that it would suck everything in the room, including the baby, down the drain when he pulled the plug. A bit of hyperbole, but he got the message.
     
  9. harrygbh

    harrygbh New Member

    Joined:
    Sep 24, 2017
    Location:
    New york
    Well why would that suddenly happen then after 40 yrs of not happening? Also if venting from rooftop is clogged wouldnt
    all fixtures in house regardless of floor have sewer smell. Wouldnt all traps get sucked dry when toilet flushes
     
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