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Thread: Single to Double vanity

  1. #1
    DIY Junior Member mfl's Avatar
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    Default Single to Double vanity

    I have been reading the posts on this site for many years and have found the discussions not only educational but entertaining. I'm changing my single sink to a double sink vanity. I've done my research and Figure 3 is what I think I need to do for a properly draining, non-smelling bathroom based on a modified Terry Love design. This will all be buried in a non-load bearing wall of a 8 year old house. Have I used the right combination of ABS tee and wye fittings for the job?
    At first I was going to use a double wye but I'm afraid of making a "S" trap situation. Secondly, I have no room for a cleanout in or under the vanity.

    This illustration represents the current lavatory / vanity set up.
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Size:  2.5 KBFigure 1 This is the current set-up as performed by a licensed plumber.
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    Figure 2
    Is going to 1 1/2" pipe for the left tee going to create problems? Name:  drain2a.gif
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    Figure 3
    I think that this is my best option. I think the 3" tee is going to drain better, help prevent clogs and be a better vent.

    Providing that you find no faults and approve of my plan... I ask if the extra 3" drain run going to perform it's function better than going to 1 1/2" as in Figure 2 or will I just be throwing my money down the drain? What do you think?

    Thank you and cheers.
    mfl
    Last edited by mfl; 05-27-2011 at 05:25 AM. Reason: word breaks

  2. #2
    Consultant cwhyu2's Avatar
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    Default

    Picture # 2 looks just fine,no need for the extra 3 inch.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Figure 2 is all you need, and even that is "overkill". If this is a bath on a slab floor, then the 3" should have a cleanout tee below the sink connections. A back to back fixture fitting, NOT a double Y NOR a sanitary cross, will accomplish the task without a lot of repiping.

  4. #4
    Forum Admin, Expert Plumber Terry's Avatar
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    I vote for the double fixture fitting, 2" x 1.5" x 1.5" x 1.5"
    Or figure 2 works too, but with more fittings.
    Really the only reason for figure 2 would be if you only had a 1-1/2" pipe to start with. Since you have a 3" line, all of your possibilities are open to you.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Here it would probably have to be 2 x 2 x 1 1/2 x 1 1/2 since it may also be the toilet's vent.

    Good point. I wasn't thinking downstream about the possiblity of it being a toilet vent.
    Terry
    Last edited by Terry; 05-27-2011 at 02:12 PM.

  6. #6
    DIY Junior Member mfl's Avatar
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    Thank you for your help.

    The double vanity that replaces the single vanity is a 350 pound beast. The master bathroom is on the second floor over a garage that has the spray foam insulation on the ceiling which not only provides a continuous vapour barrier, it also inhibits access to the pipes and drains. There's an 3" (at least) ABS vent sticking out of the roof immediately over the area in question and I ruled out the cleanout because there's no room for it...


    Now, If I understand you correctly, you are saying that figures 2 & 3 will work, but it's over engineered for the task but I'm not sure what your suggestions mean.

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    Or are you suggesting that I can lose the vent as well?

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    Would the 3/4" rise over 3 feet potentially create an S Trap in either scenario?
    Which one, if any, is correct?

    Thank you, mfl
    Last edited by mfl; 05-28-2011 at 07:18 AM. Reason: Brevity

  7. #7
    DIY Junior Member mfl's Avatar
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    Bump. Can anyone help me out?

    Thank you

  8. #8
    Forum Admin, Expert Plumber Terry's Avatar
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    Standard grade is 1/4" per foot.
    As long as your trap arms are this long are shorter, you are fine.

    1.5", 42" long trap arm
    2.0", 60" long trap arm
    3.0", 72" long trap arm

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Figure #6 is perfect, if you do not need the vent riser to be 2". And since it is a second floor you do not need a cleanout in the 3" riser.

  10. #10
    DIY Junior Member mfl's Avatar
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    You've been a great help....


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    and keep well.

    mfl

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