Single sink vanity conversion to double sink

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jamesk

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I in the process of replacing my existing single sink vanity with a new double sink vanity and need some advice on the correct way to modify my plumbing setup to allow both sinks to have the proper venting. I read through some threads with some example photos of double sink setups but I'm not 100% sure how to apply that to my current setup. I'm in Cincinnati, OH and the house is about 10 years old. I opened the wall and took the attached photo of my current setup. When looking at the photo, there is a toilet on the other side of the wall on the left and a tub to the left of the toilet. I would appreciate if someone could take a look and let me know the right way to change my current setup to a double sink setup. Thanks!
IMG_20170303_234103.jpg
 

Cacher_Chick

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You can jog the existing drain and vent over and then back to the existing stack. The rest of the drywall will need to come down to bring the vent over to the new basin.
 

Terry

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single_to_double_lav.jpg


You have 1.5" pipe coming up. They don't have a 1.5" double fixture cross that works for that.
I prefer to keep the lavs seperate, using santees, Venting each one and then tying the vents back at 42" above the flood level of the countertop.
 

jamesk

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Is this what I need to do? Sorry for the crappy drawing, I did that on my phone. I was trying to show an added tee under the existing tee at the drain/vent and running a drain arm from the lower tee over to the right side sink. Before the last elbow for the right sink drain, add a tee with a vent going up, back to the left and tieing back into the vent stack with another tee. Then shortening the existing drain arm to where the left side sink would be. Would that be proper? Also in that example, am I understanding correctly that the the added vent for the right sink would have to rise 42" from the sink before turning horizontal back to the existing vent stack? Thanks guys!
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Terry

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Santees on the vertical, and combo on the horizontal for the vent on the far lav.
Yes, that would work.
What is the counter height, and does it have a drawer below. That seems to becoming a common thing.
 

jamesk

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The actual cabinet is 34.5"tall plus another 1.5" of height for the countertop. The vanity does have drawers but only in between the two sinks. Attached is a pic.
IMG_20170304_195657_01.jpg
 

jamesk

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I see now that the 42" comes from 6" above the top of the countertop. Can you check the attached picture and let me know that the fittings are in the correct orientation? Thanks!
vanity.jpg
 

clix

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I see now that the 42" comes from 6" above the top of the countertop. Can you check the attached picture and let me know that the fittings are in the correct orientation? Thanks!View attachment 38644

I'm the last person to be giving advice, so wait for one of the pros to answer, but I think the top san tee is upside down and the combo should be turned so that if liquid gets into the second sink vent, it will be directed to flow down the drain.
 

jamesk

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That makes sense. I've updated the photo. Can someone confirm that the second photo is correct? Thanks
vanity.jpg
 

jamesk

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When I cut more of the wall out, I see that the vent already makes a 90 horizontal at 42" centered from the floor. To replace that existing elbow, I think I need a combo since it's already horizontal, is that correct? Is my orientation and type of fittings proper in the second pic?
vanity 3.jpg
vanity 4.jpg
 

Cacher_Chick

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The only one that was ever wrong was the lower right fitting, which you corrected.

On the upper left, you can use a sanitary tee, a combo, or a vent tee. Because it is not being used as a drainage fitting, any of them would be ok.
 

jamesk

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Thanks guys! Here's what I ended up with. Is it required to split the hot and cold stubs inside the wall or is it OK to put a tee on each existing stub once it passes into the cabinet?
IMG_20170305_222113.jpg
 
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