validating & choosing design to go from single to double vanity


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Old 07-11-14, 05:43 PM
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Question validating & choosing design to go from single to double vanity

Hi. I’m converting a single vanity to a double, and need some help a) validating that two design options could theoretically work, and b) choosing which solution is best.

Background:
- stack/drain is 3”, and existing trap output pipework is 1 ½”.
- I can run pipes along the floor because of the height of the new vanity (and the fact that you can’t see underneath it because of the vanity’s design).

Solution A:
Splice (probably wrong term for plumbing, but I’m used to it from electrical work :-) ) the output from the [new] left sink’s trap into the main waste/vent pipe, downstream from the existing/right sink’s output. In the green circle in the picture I’d replace a section of the 3” drain with a 3x3x1.5 wye + 45 degree bend, run that along the wall to the section circled in blue which is a 45 deg horizontal bend going into a 90 degree horizontal-to-vertical bend [and then up to the output of the trap]. My immediate question on this solution is if the proposed design in the blue circle is OK?


Solution B:
Cut out the sanitary tee (3x3x1.5) circled in red, and replace with a double sanitary tee (3”). The new double sanitary tee would hook back into the existing piping on the right, and then I’d ~ mirror that piping on the left side going out to where the left sink will be. My main ~ concern here is that I can’t find a 3x3x1.5x1.5 PVC double sanitary tee (or double fixture tee) nearby, so I’d have to put in some reducers (in reverse) to go from 1.5” to 3”.


Could either of these work? Is there an even better option out there? Any recommendations on which solution to go with?

P.S. If I should go with B, do you think it's important enough to order and double fixture tee online and just wait for it to get here?

Thanks in advance!
 
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Old 07-13-14, 06:34 AM
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I vote for B. If you have another bathroom, order online.
 
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Old 07-18-14, 10:06 AM
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Just wanted to chime in that your option A wouldn't work unless you want to vent that line. You'd have to cut out the wall and vent up to the roof or back-vent it and connect it to the existing vent stack at least 42" high.

I agree with Pulpo, a double san tee would do what you want. Add in two 3"no-hub couplings and you should be done easily and quickly!
 
 

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