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Thread: Can a main stack have a curve

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    Default Can a main stack have a curve

    We had a second floor put on our house and in doing this, they built the walls for two bathrooms and roughed in the plumbing for one of them. I started preparing to build out these bathrooms and seen the cut the main stack just before it went into the second floor and put a 90 on it with a curve then a straight and then a T and then they put it up through a wall on the second floor and through the ceiling. the main stack was a 4" main and now it is up to the 90 - it is a 3inch from there to the T from the T up through the roof it is a 2".

    Question 1: is a main stack allowed to go from a 4" to a smaller diameter
    Question 2: is a main stack allowed to be cut and relocated like that?
    Question 3: where they have the 90 and the curve - is that allowed or should
    that be a sweeping connection

    Thanks in advance for all your help !!

    Steve

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    Moderator & Master Plumber hj's Avatar
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    Default ?

    quote; Question 1: is a main stack allowed to go from a 4" to a smaller diameter
    Question 2: is a main stack allowed to be cut and relocated like that?
    Question 3: where they have the 90 and the curve - is that allowed or should
    that be a sweeping connection

    1. Usually yes, but the individual situation would determine whether it is proper or not.
    2. Again normally Yes, but exactly how they did it could be a factor.
    3. A sweeping connection going up, a "short radius" going down is acceptable.

    NOW, the big question is; WAS that pipe originally the "vent" for the downstairs bath, and if so, is it still the vent? If yes, then NOTHING they did may be proper or approved. You are asking questions that should have been addressed by the plumbing inspector when he approved it.

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    Thank you for the answers. Yes, that was and is the vent for the downstairs Bathroom, I had replumbed it about a year ago moving the toilet about 6 ft to the other end/side of the bathroom. I replumbed it using 4" sch 40 PVC and it is about 8ft from the stack, the stack is suppose to be it's vent. I relooked at the connection they did and it is a short sweep using 3" pipe with an adapter to the 4" pipe. The distance from the stack to the now 2" pipe that goes up through the ceiling is about 28". From the T where it goes up through the ceiling, the 3" pipe then travels on to the roughed in toilet flange for the one upstairs bathroom. Now I was going to create 4 vent lines into one to attach the two sinks and tubs from the two bathrooms upstairs to either the stack vent in the attic or to their own vent through the roof and I was also going to attach a line to the 2nd bathrooms toilet run due to distance from stack, would that work?

    As for approved by the inspector, we were not there when it was done and I do not believe they had an inspection, that is why I am asking this, so that I can redo it if necessary and then have it inspected.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Can you attach some photo's?

    800 pixels or less, and less then 100KB

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by millers_7 View Post
    We had a second floor put on our house and in doing this, they built the walls for two bathrooms and roughed in the plumbing for one of them. I started preparing to build out these bathrooms and seen the cut the main stack just before it went into the second floor and put a 90 on it with a curve then a straight and then a T and then they put it up through a wall on the second floor and through the ceiling. the main stack was a 4" main and now it is up to the 90 - it is a 3inch from there to the T from the T up through the roof it is a 2".

    Question 1: is a main stack allowed to go from a 4" to a smaller diameter
    Question 2: is a main stack allowed to be cut and relocated like that?
    Question 3: where they have the 90 and the curve - is that allowed or should
    that be a sweeping connection

    Thanks in advance for all your help !!

    Steve
    1. Not in the direction of flow it can't.... but it can go from smaller to bigger.
    2. Usually yes.. How far are you offsetting? Depending on the piping configuration (and doubtful) you may need an offset relief vent.
    3. If the main stack is 4" (or larger) according to the Canadian NPC you are allowed to use 90's however you want... If the main stack is 3" you have a few rules you need to stick too. However sweeping connections are always preferred if practical.

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    Ok - I do not have pics right now, but I did the attached drawing in MS paint - see if this is clear enough, if not I will try and get pics tomorrow...thanks
    Attached Images Attached Images  
    Last edited by millers_7; 12-29-2009 at 02:04 AM. Reason: tried to make picture a little clearer

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    thanks for the reply !! you can see the attached document on the previous reply to see the configuration. I believe that from what you said the vent they did is okay - the pipe never gets smaller for the waste, it goes bigger, just the vent pipe was change from a 4" to a 3" then a 2". The offset is only about 26-28". Thanks again

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