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Thread: Can I Tie A Sink Drain Into A Floor Drain Vent Line?

  1. #1

    Default Can I Tie A Sink Drain Into A Floor Drain Vent Line?

    I would like to put a utility sink in a particular location in my basement. There is a floor drain near the planned sink location. The vent pipe for the floor drain runs up a nearby interior wall a couple of feet from where I would like to place the sink. The drain connects to the septic system.

    Can I safely tee into the vent stack and connect the sink's trap to that point?

    Thank you.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Generally, once you make a vent a drain, it no longer functions as a vent, so no. You'd have to tie into the drain line before the vent take-off fitting. You could connect to that vent above the flood plane of the new sink so you don't have to run a new vent line, though.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    The vent take off fitting is embedded in the basement floor. I was hoping what I would like to do constitutes a wet vent.

  4. #4

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    Quote Originally Posted by Cedar
    I was hoping what I would like to do constitutes a wet vent.
    You're in luck! It does constitute a wet vent.

    That's what's wrong with it.

    Whether you can do what you want to do depends upon your local code and how it is enforced.

    For example: in the Uniform Plumbing Code, you can wet vent a toilet with a basin drain, but the required vent (2") has to be raised to the next pipe size when you do (3" assuming there is no 2-1/2" pipe available).
    Steve's Plumbing Service

  5. #5
    Master Plumber nhmaster's Avatar
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    Quote Originally Posted by Lakee911 View Post
    Is it right? No. Will it work? Probably.
    Well, yea but that can be said for probably 90% of wrong plumbing.

    You can only wet vent bathroom groups (fixtures) no kitchen sinks, laundry trays, washing machines etc.

  6. #6
    Plumbing Designer FloridaOrange's Avatar
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    Quote Originally Posted by nhmaster View Post
    You can only wet vent bathroom groups (fixtures) no kitchen sinks, laundry trays, washing machines etc.
    I am very familiar with that rule but not the reasoning behind it, any insight? It makes it a pain when trying to add a drinking fountain to a small commercial space.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  7. #7
    Plumber Cass's Avatar
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    If what you will be washing down the sink you could just as easily pour down a floor drain then you could install a utility sink and make the drain to the floor indirect...you would be giving your self a sink to splash in and just dumping rinse water down the floor drain...that would also keep it from drying out...if you are dumping any sort of industrial waste...don't do it...

  8. #8

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    Thanks for the replies.

    The sink will mostly be used for washing up. Nothing will go down the drain that isn't septic system safe. Unfortunately, the floor drain is in the walkway part of the room, a home workshop.

  9. #9

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    Quote Originally Posted by nhmaster View Post

    You can only wet vent bathroom groups (fixtures) no kitchen sinks, laundry trays, washing machines etc.
    So, if I mount a urinal on the wall next to the sink, it would be OK?

    I can just imagine my wife's reaction the first time she ses it.

  10. #10
    DIY Senior Member seaofnames's Avatar
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    Quote Originally Posted by Cass View Post
    If what you will be washing down the sink you could just as easily pour down a floor drain then you could install a utility sink and make the drain to the floor indirect...you would be giving your self a sink to splash in and just dumping rinse water down the floor drain...that would also keep it from drying out...if you are dumping any sort of industrial waste...don't do it...
    Thats kind of what I was thinking. According to most of the stuff I've seen/worked on, floor drains(especially in bathrooms) are 'emergency' so they aren't accounted for in the total number of fixtures. Obviously, we arent anywhere near the limit of fixtures, so there is always a safety factor, but if it really came down to it...the floor drain is only an emergency drain!

    At least thats how it is here in BC!

    And the usual..it depends on which code you are using or what your inspector says.

  11. #11
    Master Plumber nhmaster's Avatar
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    If you use a lav and not a utility sink then , yes, you can wet vent it along with a urinal.

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