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Thread: Question about adding a new sink to my basement using existing line.

  1. #1
    DIY Junior Member ddaniels's Avatar
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    Default Question about adding a new sink to my basement using existing line.

    Rookie question.

    I have a 1 1/2inch drain line that drains my kitchen sink on the main level of my house and runs through the basement into the ground. I need to know if I can add a bar sink to the exisitng drain. I have attached a photo to show my situation.
    Please let me know if this is possible or if you have any other suggestions.
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    Thanks.

    Darren

  2. #2
    DIY Junior Member Ottawa97tj's Avatar
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    Hang in there a pro will confirm soon but from what I understand you can't do it the vent would have to be above the highest fixture in the line, if nothing is above the kitchen sink then the vent would have to tie in there

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    Forum Admin, Expert Plumber Terry's Avatar
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    Not without a vent.
    When the upstairs drains, it will push air out of the trap below.

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    In the Trades Tom Sawyer's Avatar
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    To do it right you would have to increase the drain size to 2" to the point the bar sink connects and properly vent the bar sink. An AAV may be allowed in our jurisdiction.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    DIY Senior Member asktom's Avatar
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    An AAV won't protect against positive pressure (that air being pushed down from the sink above).

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    In the Trades Tom Sawyer's Avatar
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    Hence the need to increase the drain to 2"
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  7. #7
    Moderator & Master Plumber hj's Avatar
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    Connecting the vent back to the drain line WOULD work, but it would also be illegal. It has to tie in at a point above the sink on the upper level. Positive pressure is positive pressure whether the drain is 1 1/2", 2", OR 3".
    Licensed residential and commercial plumber

  8. #8
    Forum Admin, Expert Plumber Terry's Avatar
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    Connecting the vent back to the drain line WOULD work, but it would also be illegal.
    If it were to be added to the waste stack, it would need to be done is such a way that no waste comes down the vent portion. It would need to be treated like an island fixture.

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