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  • roof vents

    hi all, i have 3 sewer vents extending through my roof, two 2 inch and a 3 incher.as i am re roofing my house i was thinking i could tie the 2 smaller ones into the bigger one and have less leak prone areas to worry about as we get lots of rain to deal with here.

    thanks

  • #2
    Re: roof vents

    Sounds good to me
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    • #3
      Re: roof vents

      Simply too much work.
      Proud To Be Union!!

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      • #4
        Re: roof vents

        Agree with Aaron, it's probably easier to put three new flashings on than tie those vents together. A properly installed flashing should last as long as the shingles...unless its lead and the squirrels start gnawing on it.
        "When we build let us think we build forever. Let it not be for present delight nor for present use alone. Let it be such work that our descendants will thank us for, and let us think, as we lay stone upon stone, that a time is to come when these stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, "See! This our fathers did for us."
        John Ruskin (1819 - 1900)

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        • #5
          Re: roof vents

          If all the vent are tied into together then you'll put a plumber at a real disadvatage if he ever has to snake your line through the vent. Sometimes that's the only way. He'll make sure he get "compensated" for the difficulty.
          Buy cheap, buy twice.

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          • #6
            Re: roof vents

            I just did one that they put a "T" in and it cost em $500 by the time I got done. If your not a plumber dont screw with the vents!!!!!!
            http://www.all-clear-sewer.com/

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            • #7
              Re: roof vents

              It's not like you have 8 vents going through the roof, you only have 2- 2" and 1 - 3" I would just leave then and make sure your roofer does his job properly.

              The other thing, if you have a 4" sewer, you need a certain amout of air in your sewer for it to drain properly and keep the trap seals, when you shrink the vent area, you shrink the sewer area and can cause trap seals to siphone among other problems. Here is mathmaticaly why you cannot do it:

              On a 4" sewer, you need 12.56 area, so lets assume with 1-3", and 2-2" you have a total of 13.34 area, now, let's say you need 12.56, if you lose one of those 2" vents, (1-3" and 1-2") it cuts you down to 10.20 area, if your main is 4", you need 12.56, you are 2.36 short.

              If you have a 3" sewer, you need 7.06 area. and you can tie both those 2" vents into 3", but then you run into the snaking problems etc, if you don't have a c/o.

              Wordy, but if you read it a few times and do the math, you will get it.
              Last edited by westcoastplumber; 07-18-2007, 09:20 PM.
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              Robert

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              • #8
                Re: roof vents

                Originally posted by westcoastplumber View Post
                It's not like you have 8 vents going through the roof, you only have 2- 2" and 1 - 3" I would just leave then and make sure your roofer does his job properly.

                The other thing, if you have a 4" sewer, you need a certain amout of air in your sewer for it to drain properly and keep the trap seals, when you shrink the vent area, you shrink the sewer area and can cause trap seals to siphone among other problems. Here is mathmaticaly why you cannot do it:

                On a 4" sewer, you need 12.56 area, so lets assume with 1-3", and 2-2" you have a total of 13.34 area, now, let's say you need 12.56, if you lose one of those 2" vents, (1-3" and 1-2") it cuts you down to 10.20 area, if your main is 4", you need 12.56, you are 2.36 short.

                If you have a 3" sewer, you need 7.06 area. and you can tie both those 2" vents into 3", but then you run into the snaking problems etc, if you don't have a c/o.

                Wordy, but if you read it a few times and do the math, you will get it.
                grasshopper, with answers like that, you'll be moving up to master grasshopper real soon

                true, you need the same amount of cross sectional area as the sewer that leaves the building. so robert, although a little confusing in his explanation, he is correct

                now as a practical explanation goes. as others here have mentioned, you can never have enough vents, especially if you need to snake from a roof vent. i would extend them all through the roof. you've already got plenty of vents tied together with only 3 vents now.

                all get a thumbs up

                rick.
                phoebe it is

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                • #9
                  Re: roof vents

                  Originally posted by PLUMBER RICK View Post
                  grasshopper, with answers like that, you'll be moving up to master grasshopper real soon

                  true, you need the same amount of cross sectional area as the sewer that leaves the building. so robert, although a little confusing in his explanation, he is correct

                  now as a practical explanation goes. as others here have mentioned, you can never have enough vents, especially if you need to snake from a roof vent. i would extend them all through the roof. you've already got plenty of vents tied together with only 3 vents now.

                  all get a thumbs up

                  rick.

                  Thanks Daddy, I told you I have a hard time putting things into words My brain moves faster then I can write or type.
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                  Robert

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                  • #10
                    Re: roof vents

                    ok...lost here on the vent thing...we simply require a 3" main to be 3" all the way through the roof..a 4" the same and so on.

                    To me with a 4" requiring 12.56 area...a 4" would be the area of a 4" (4 x 4 x .7854)...why not just say 4"?

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                    • #11
                      Re: roof vents

                      Well here I go not being a plumber but questioning two excellent plumbers opinions.
                      I get that Area = π r² but practical experience tells me you need far less cross sectional area to let enough air in for a given cross section of fluid output. Consider the lowly gas can, it has a relative pin hole size air input compared to the gas output and yet it does not lack for air flow to allow full gasoline flow.
                      I may be wrong but please tell me why.
                      Not questioning the logic behind more vents for snaking that makes perfect sense
                      Last edited by wbrooks; 07-18-2007, 09:44 PM. Reason: content

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                      • #12
                        Re: roof vents

                        It's about having equal air pressure on both sides of a P-trap to prevent siphonage.
                        Brent

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                        • #13
                          Re: roof vents

                          Originally posted by BAPlumber View Post
                          It's about having equal air pressure on both sides of a P-trap to prevent siphonage.
                          dude, thats what I mean't, just in a round about way
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                          Robert

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                          • #14
                            Re: roof vents

                            Robert, the funny thing is I read your post and said you must have quoted the code book

                            Joey
                            I love my plumber

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                            Welcome, Phoebe Jacqueline!

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                            • #15
                              Re: roof vents

                              Originally posted by westcoastplumber
                              I am sure the system will operate on less area, but according to the UPC, the minimum standards were listed, I am not an engineer, it may work on less, according to the gas can example. I quoted the minimums, which I am required to adhear to
                              soon you will not be waxing my cars you will be telling others what to wax master grasshopper

                              as per the upc code book. the cross sectional area of the building sewer has to have an equal or more cross sec. for the roof vents.

                              there are times when the sewers have a positive and a negative pressure. it all equals out this way. now with jetters, the more venting, the better.

                              rick.
                              phoebe it is

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