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  1. #1
    Join Date
    Oct 2008
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    ca
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    3

    Question dual sink plumbing

    Am renovating a master bathroom in an 80's home. There is currently one sink. I want to install 2 sinks. There is room on the existing cabinet.

    What I would like to do is tee off the existing hot and cold water supply lines and connect both sinks. The existing supply lines each have a shutoff valve. Don't really want to remove sheet rock and redo existing in wall water lines.

    The only drawback I can think of is will there be too little water supply if the faucets in both sinks are turned on simultaneously.

    Any thoughts on my plan?

  2. #2
    Join Date
    Feb 2010
    Location
    South*East
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    1,183

    Default Re: dual sink plumbing

    The water supply isn't the problem the waste line is. If your thinking you can just install a tee under the cabinet and connect the two sinks together there is a good chance when you drain one sink it will siphon the trap on the other. In most cases to do it correctly you will have to open the wall up.

    John

  3. #3
    Join Date
    Jul 2010
    Location
    SoCal
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    5,436

    Default Re: dual sink plumbing

    Ideally, all connections should be in the wall: hot/cold supplies and drain. To do that, you will need to cut the drywall out. It's no biggie, and it's probably invisible inside the vanity or cabinet.

    Hot/cold supplies: if you run them off the other sink, your water pressure will be lower when both faucets are turned on since they're probably only 1/2" lines.

    Drain: If you tie in the other faucet's drain, do it at the lowest point possible.

  4. #4
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,418

    Default Re: dual sink plumbing

    You could potentially do the drains the same way you'd hook up a double-basin kitchen sink: feed into a tee, then into a trap then into the wall.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  5. #5
    Join Date
    Feb 2010
    Location
    South*East
    Posts
    1,183

    Default Re: dual sink plumbing

    Quote Originally Posted by Fencepost View Post
    You could potentially do the drains the same way you'd hook up a double-basin kitchen sink: feed into a tee, then into a trap then into the wall.
    Code requires a separate trap for each fixture.

    John

  6. #6
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,436

    Default Re: dual sink plumbing

    Fence -

    A double kitchen sink is not like two separate sinks close together.

    The kitchen sink has only one faucet.

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