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Thread: Remodeled Bathroom Venting

  1. #1

    Default Remodeled Bathroom Venting

    I have a 50 year old ranch with 2 full baths (A and B), one of which I have gutted and am remodeling (B). Bath (A) has a 3" copper waste line for the sink, toilet, & tub and vents thru a 3" stack. This same waste line runs about 15 (linear) feet where tub (B) ties in and the whole thing empties into the cast iron main drain. There is a second 3" waste line for the sink and toilet in (B) that is vented by a second 3" stack. This line ties into the cast iron main drain about 4' above the one from (A).

    Originally, the 3" vent in (B) ran thru a closet wall and was at the end of the run. That closet is now gone. I removed all the fixtures and the 3" vent pipe and reconfigured it as follows: I connected a 3" wye (with a 2" branch) to the cast iron main with a rubber clamp-coupling. I will run 3" PVC to tie in the toilet and sink which are 3' apart and 18" from the wye. I replaced the 3" copper vent with 2" PVC coming off the wye and going up thru the attic to the roof. Here is my question: is this enough venting for the sink and toilet or did I make a huge mistake by using only 2" pipe? I figured the other vent was already handling the other fixtures and reducing vent (B) wouldn't really make that much difference. I haven't sealed up the walls yet so I can change it if I need to.

    Please let me know if this is OK. Any/all advice I can get would be greatly appreciated.

  2. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default Piping

    Which fittings you used may be less important than how you used them and we cannot tell that without a picture to see if they are oriented properly. Normally as long as the total area of the pipes through the roof are equal to the area of the main line into the building, you have adequate venting.

  3. #3


    Thanks for your reply HJ. Please forgive my ignorance but this is uncharted territory for me. When you say the main line into the building, do you mean the supply line or the waste line? There is a 3/4" supply line coming into the house and a 4" waste line going out to the city sewer system. Below is the "Before & After" drawing I made. Maybe that will help clarify things. Thanks again.
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