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Replacing verticle vent pipe that runs above roofline, can I substitute 4" with 3"?

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  • Replacing verticle vent pipe that runs above roofline, can I substitute 4" with 3"?

    I had a 4" cast iron vent pipe running up the side of my house and when the roofers replaced my roof, they forgot to re-attach it...it spun in one of the joints and came down, so I removed it, as I was replacing much of it with ABS anyways.

    Any reason why I can't replace the 4" verticle vent with 3" ABS?
    In our city, 3" is acceptable for code.
    Would 3" vent effect performance of drainage, or flush, as a toilet will be just below?

    Thanks for the help!

    Rick

  • #2
    Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

    What all is vented by this vent?
    Are there any other vents on the house?

    Generally I don't like to reduce vents in size, but I don't think that it would be against code.
    Your house would function
    well with a 3 inch vent but code is the real issue.
    THe other is that it may look odd,

    Michael

    Comment


    • #3
      Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

      In MD, one 3" is reguired. In some counties on septics years ago once the 3" went into the attic they would make us increase to 4" through the roof. I belief because of the septic relief vent. It had to go to the attic and back vent into the 3" only( very last back vent ) then 4" through the roof. Seems that all counties make their own rules at times .
      The Plumber/Firefighter

      Comment


      • #4
        Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

        the roofers "didn't forget it" they didn't want to deal with it. so they left it off. if you haven't paid them yet, well "forget to" pay them until they make it right. roofers. breid................

        Comment


        • #5
          Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

          Here it all depends how many fixture units are being vented on that line.

          Comment


          • #6
            Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

            Originally posted by Flux View Post
            Here it all depends how many fixture units are being vented on that line.
            That's true here as well but always had their funny ways with the septic relief vent. The 2 " septic relief vent was the first thing added after clean out. Some would let you pick up one wet fixture ( vanity ) and others said it had to be dry all the way.
            The Plumber/Firefighter

            Comment


            • #7
              Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

              Originally posted by Fred the plumber View Post
              That's true here as well but always had their funny ways with the septic relief vent. The 2 " septic relief vent was the first thing added after clean out. Some would let you pick up one wet fixture ( vanity ) and others said it had to be dry all the way.
              I swear conflicting Plumbing codes really irk me sometimes. Besides the common sense issues with our codes, I honestly believe everything else is nothing but a farce.

              Comment


              • #8
                Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                Originally posted by Flux View Post
                I swear conflicting Plumbing codes really irk me sometimes. Besides the common sense issues with our codes, I honestly believe everything else is nothing but a farce.
                I totally agree with you. Sometimes I call the Chief or an inspector to clarify something because lots of things that counties require are not always answered in the code books. It's also funny how one area requires something totally different. It's all a joke at times and job justification. It's like my Fire Departmet, we have 6 battalions in the city which equates to 6 different Fire Depts. Makes me sick. Uniformity should be mandatory for the most part but it's not.
                The Plumber/Firefighter

                Comment


                • #9
                  Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                  There is a 4" vent on the other side of the house that vents a downstairs bathroom, kitchen and laundrey, continues through to the second floor and also vents the upstairs bathroom.

                  The second vent, comes from the basement and only vents the basement bathroom.

                  I am remodeling the house, and changing the layout of rooms.

                  The 1st vent I mentioned above, when the remodel is done, will only have the kitchen and upstairs bathroom on it.

                  The 2nd vent in the basement, which comes out of the basement floor about 3" from the basement toilet, will have added to it the 1st floor bathroom, and the wash machine. It will also include the existing basement bathroom.

                  Actually what I did, was take the vent where it comes from the basement floor, and instead of it venting directly outside, I am adding the 1st floor bath and wash machine.

                  Sounds like I need to keep the vent at 4"...not a problem, just would be less conspicuous at 3".

                  Thanks for all the posts!

                  Rick

                  Comment


                  • #10
                    Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                    According with the IPC you could probably get away with a 2" vent if you already have a 3" stack vent through the roof...go figure ..Hell here you could probably studer vent it and be done
                    ''Beer is proof that God loves us and wants us to be happy" Benjamin Franklin

                    Comment


                    • #11
                      Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                      Originally posted by rich121 View Post
                      There is a 4" vent on the other side of the house that vents a downstairs bathroom, kitchen and laundrey, continues through to the second floor and also vents the upstairs bathroom.

                      The second vent, comes from the basement and only vents the basement bathroom.

                      I am remodeling the house, and changing the layout of rooms.

                      The 1st vent I mentioned above, when the remodel is done, will only have the kitchen and upstairs bathroom on it.

                      The 2nd vent in the basement, which comes out of the basement floor about 3" from the basement toilet, will have added to it the 1st floor bathroom, and the wash machine. It will also include the existing basement bathroom.

                      Actually what I did, was take the vent where it comes from the basement floor, and instead of it venting directly outside, I am adding the 1st floor bath and wash machine.

                      Sounds like I need to keep the vent at 4"...not a problem, just would be less conspicuous at 3".

                      Thanks for all the posts!

                      Rick
                      From what you described 3" is more than enough to vent the Kitchen and bathroom. Now someone correct me if I'm wrong, but that's 8 D.F.U.'s and 1 3" stack is good for 20 D.F.U's.

                      Comment


                      • #12
                        Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                        All you're doing is reducing the size of the stack, right?
                        It's still 4" at least up to the floor, right?
                        Which means it will be drawing plenty of air, right?
                        You could run a 2" riser with no problem, so I'm certain
                        a 3" would suffice, right?
                        As for the code...fugeddaboutit.
                        There won't be an inspection or permit, right?

                        Comment


                        • #13
                          Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                          Originally posted by Big Jim View Post
                          All you're doing is reducing the size of the stack, right?
                          It's still 4" at least up to the floor, right?
                          Which means it will be drawing plenty of air, right?
                          You could run a 2" riser with no problem, so I'm certain
                          a 3" would suffice, right?
                          As for the code...fugeddaboutit.
                          There won't be an inspection or permit, right?
                          Thanks....the fugeddaboutit made me chuckle.
                          Ideal Plumbing

                          Comment


                          • #14
                            Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                            Just use 4 " ! I don't use 14/2 on a 20 amp circuit.
                            I can build anything You want , if you draw a picture of it , on the back of a big enough check .

                            Comment


                            • #15
                              Re: Replacing verticle vent pipe that runs above roofline, can I substitute 4" with

                              Originally posted by toolaholic View Post
                              Just use 4 " ! I don't use 14/2 on a 20 amp circuit.
                              Well, since you want to talk electrical, there is always going the next size down for the neutral in a service, or the smaller sizes of conductor for the ground..etc.... in certain circuits, such as welders, you can use 30A wire for a 60A welder due to duty cycle...many other exceptions, rules, code etc. for other circuits...

                              I'm asking because I want real world, not some smart *** comment ...as with any trade, there are exceptions, calculations, standards etc.

                              Comment

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