Quick sink drain question

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Murpy

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Hey all, new member here.

Been reading and learning alot, and realizing the guy I've been using for plumbing has made some mistakes in the past...but Im currently doing my own DIY bathroom and wanted to see what the deal is with this drain before I put up drywall

Backstory: The 4" veritical pipe you see here is the only waste pipe and vent in the entire house. There's this 2nd floor full bathroom and a half bath right under it. The pipe up goes straight out the roof.

At one time, this was all cast iron, had the same kind of Wye in cast, and the sink drain was lead. It ran thru the studs in the same configuration as you see since the house was built in 1952.

A few years ago the 4" cast cracked and i had a guy replace it with the PVC. We didn't mess with the lead sink drain and he basically used a Fernco coupler with the 2 clamps and it never gave me a problem.

Now we're current. I did the PVC part of the drain, its basically a clone of how it was in lead. I posted this on Facebook and a bunch of armchair plumbers are telling me I need vents, and that it needs air. I think that part is fine, Im more concerned about the drop and the vertical wye.

Ive read too much and have confused myself. Does that Wye need to be a sanitary tee? I didnt know if that applied to me since I have that drop and it doesnt meet horizontally.

So before I put the drywall on, I need to get confirmation one way or the other.

This is how it used to be from the other side

Heres when we originally changed to PVC, you can see the original lead drain for the sink and how it was run
 
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hj

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It DOES apply to you. You need a sanitary tee, but it MUST be located higher so it goes to the right and ends at the sink with an elbow.

lav_rough_1.jpg
 
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Murpy

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Thanks for your answer and confirming that I have thought/read, but Im still unsure why what I have is no good. Perhaps it's against modern day code but it's a clone of what was there for 65 years. Whats the technical reason behind it?

Appreciate your reply.
 

Reach4

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Whats the technical reason behind it?
You don't currently have a vent before the drain turns down. Therefore the water from the trap can siphon out and let sewer gasses into the room.

You could, as an alternative to the sanitary tee, add a vent to each drain line before it turns down.
 
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Murpy

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Could I just leave that Wye in there and cut & cap that 1.5" pipe? Then install a San T a higher up, giving it 1/4" per foot slope from the sink?
 

hj

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if you want to. It was NOT code when it was installed either. For what its worth, I have been doing plumbing for 65 years and it was NOT code when I started, or even 40 years before that.
 
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