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  • Venting question

    Hello:

    I am by no means a plumber so am looking for some advice.

    I've lived in my current home about 1.5 years, today I noticed a sewer gas smell in an upstairs bathroom. Upon further investigation it seemed to be coming from the bathroom exhaust fan. If I turned the fan on the smell went away, but came back as soon as the fan was off.

    Ascending to the attic, it appears that the 2 bathroom fans upstairs share a common vent through the roof with the waste stack.

    That seems like a problem to me but what do I know. Is that a problem? If so what't the easiest way to fix it? It probably involves a new stack through the roof for just the bathroom fans huh?

    Thanks!

  • #2
    Sounds to me like you have the polarity reversed on the bath fan and its sucking air in instead of blowing it out. Try flipping the plug on the spot where the bath fan plugs in to its rough-in box. Otherwise rerouting the bath fans to the side of the house not through the roof would be better.

    Comment


    • #3
      Originally posted by Carrie:
      Hello:

      Ascending to the attic, it appears that the 2 bathroom fans upstairs share a common vent through the roof with the waste stack.

      Thanks!
      Carrie,

      I am sure you have found both the problem and the repair already. Not only should a vent from the DWV system not share a stack with exhaust fans, the DWV vent is required to terminate 10' horizontally or 3' vertically from any opening into the structure.

      Mark

      [ 10-24-2005, 12:16 AM: Message edited by: ToUtahNow ]
      "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

      I never lost a cent on the jobs I didn't get!

      Comment


      • #4
        first off the bat, there is no reverse polarity on a bathroom exhaust fan. these are ac motors and they don't run reverse.

        2 things. #1 the bathroom exhaust vents should not be common and should never tie into a plumbing vent stack. #2- the exhaust vents typically have a flapper type check on them. make sure that they are installed at the outlet of the fan housing.

        best bet is to separate the 2 bathroom exhaust and run them separate to the outside. don't connect to a plumbing vent stack.

        out of curiousity how old is this installation? is it a track home? out here (los angeles) this was never legal.

        rick.

        Comment


        • #5
          Rick,

          The described installation is illegal under both the UPC and the IPC.

          Mark

          BTW: Even with a DC motor the polarity has nothing to do with rotation unless it is a parallel wound motor.
          "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

          I never lost a cent on the jobs I didn't get!

          Comment


          • #6
            While that is true polarity shouldn't matter, but i have seen it with my own eyes, a bath fan blowing instead of sucking. I flipped the cord and it sucked instead of blowed. Might have been bad wiring in the house. Call me crazy, but it happened. You guys are right it's not code, that thought never crossed my mind [img]smile.gif[/img] Are y'all normally shooting the fart fans out the side of the house or does anyone prefer the roof. I just think of it as one less hole in the roof and less flashing and keeping water out to work with.

            Comment


            • #7
              In residential Electrical work i always got the job of venting the "fart fans" We NEVER tied them into anything else. the easiest way was to vent them out an eve or through a wall and latter put a nice looking cover over the hose. As for the wiring all the fans i have ever done had a hot (BLACK, red or blue) neutral (White) and ground (green or bare). The age of your home is a big factor. My dad's house was originally an old army barracks and had no vent fans.
              "Diplomacy is saying nice dodging until you can find a rock." Will Rogers
              "If a Monkey can do your job, are you in the right profession?

              Comment


              • #8
                Carrie, If youre attic is vented at both ends just let the exaust from the bathroom terminate in the atic. Disconnect You're vent from the fart fan and run it out alone, seperating the two. Youre methane gas will go outside and youre fart fan gases will eventually get out as well and I'm sure you don't spend alot of time in the attic.
                christopher

                Comment


                • #9
                  Originally posted by Quescodeplumb:
                  Carrie, If youre attic is vented at both ends just let the exaust from the bathroom terminate in the atic. Disconnect You're vent from the fart fan and run it out alone, seperating the two. Youre methane gas will go outside and youre fart fan gases will eventually get out as well and I'm sure you don't spend alot of time in the attic.
                  I certainly hope you are not advising Carrie to terminate his environmental ducts into the attic. Not only is that a violation of UMC 504.1 it also has the potiental to cause damage in the attic from moisture expelled from the bathroom.

                  Mark
                  "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                  I never lost a cent on the jobs I didn't get!

                  Comment


                  • #10
                    back in the early 80's fart fans were allowed to be unducted. they had a small carbon cartridge in them and recirculated the air. eventually the city got smarter and did away with these fans. don't think anyone ever changed the carbon cartridge.

                    keep in mind that the fart fans were required in bathrooms without windows. don't know how anyone would be able to retro-fit an installation in a multilevel wood framed building?

                    glad it was the hvac's contract and not the plumbers who installed these.

                    rick.

                    Comment


                    • #11
                      Carrie, whatever you do, DO NOT vent your fans into the attic. They have to exit through the roof or through the side of the house. Venting in the attic will cause your roof to rot and cause the attic to stink, mold, mildew and every other imaginable horrible thing that can happen. [img]smile.gif[/img]

                      Comment


                      • #12
                        I have a couple of comments on this situation.

                        1) Are you sure the vent duct is connected to your waste vent? Not calling you stupid, but your post indicated that you are not a plumber. Are you sure what you are identifing as a waste vent is a waste vent? What material is it? What age is the building?

                        It is possible that it is connected to a common fart fan vent, and not a waste vent.

                        2) If the fan vent is connected to a waste vent over-head, the smell will probably not travel into your bathroom. It is possible, but not usually the case. Sewer gases are lighter than air, therefore travel upward. That is why sewer vents work on gravity.

                        3) Based on the above, I would look for the smell in your bathroom. You said when the fan is on, the smell goes away. If you are getting gas in the bathroom, of course a fan would suck it out.

                        4) Here's an experiment. Cover the fan register in your bathroom for a day. If you get a smell, it's not coming from above, but below (in the room).

                        5) If that is the case, check the traps in that bathroom. Do you have a shower/bathtub you don't use? Is there a trap leaking. Any of those will cause a smell.

                        In conclusion: If you are getting a smell, it is serious. Sewer gas is nos just annoying, but highly flamable and dangerous. Please take care of this.

                        the dog
                        the dog

                        Comment


                        • #13
                          Good points Dog. It is very possible the smell is coming from inside the room. Though I respectfully disagree about the sewer gas not being able to renter the home through the fan vent if it is connected to a sewer vent. There are several atmospheric conditions which could create a down draft and force or draw the sewer gas back down into the home.

                          A hardened and cracked toilet bowl seal can often allow sewer gas to enter the room even though the water does not. Another cause of very bad smell can be the overflow in the lavatory,this is something very often overlooked by even the most experienced plumbers. The seldom used tub in a secondary bathroom is a likely culprit as was mentioned.

                          Bathroom vents are allowed to be vented into the attic if the termination point is just below a ventilator. In colder climes the condensation created from the hot showers being vented directly into zero degree weather can run right back down a vent and into the bathroom fan. Even using insulated duct is not a fool proof way to eliminate this problem. Fortunately its not the plumbers work here to mess with these.
                          Work hard, Play hard, Sleep easy.

                          Comment


                          • #14
                            The key terms to UMC 504.1 are "substaintally airtight" and "shall terminate outside the building". A lot of sheet metal guys will run bathroom exhaust vents to within a couple of inches of a dormer vent or t-top flashing but they are suppose to be mechanically connected all the way to the outside.

                            By the way if that same vent is installed on the roof in Las Vegas, Las Vegas has an admendment which says no back draft damper is required. I always wonder how these admendments are approved and why. How does a backdraft damper hurt an environmental exhaust?

                            Mark
                            "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                            I never lost a cent on the jobs I didn't get!

                            Comment


                            • #15
                              Originally posted by plumber:
                              Good points Dog. It is very possible the smell is coming from inside the room. Though I respectfully disagree about the sewer gas not being able to renter the home through the fan vent if it is connected to a sewer vent. There are several atmospheric conditions which could create a down draft and force or draw the sewer gas back down into the home.

                              A hardened and cracked toilet bowl seal can often allow sewer gas to enter the room even though the water does not. Another cause of very bad smell can be the overflow in the lavatory,this is something very often overlooked by even the most experienced plumbers. The seldom used tub in a secondary bathroom is a likely culprit as was mentioned.

                              Bathroom vents are allowed to be vented into the attic if the termination point is just below a ventilator. In colder climes the condensation created from the hot showers being vented directly into zero degree weather can run right back down a vent and into the bathroom fan. Even using insulated duct is not a fool proof way to eliminate this problem. Fortunately its not the plumbers work here to mess with these.
                              Plumber,

                              My post indicated that it is possible, but not likely that sewer gas would float downward. I think it's something worth looking into.

                              the dog
                              the dog

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