Adding new sink drain to existing horizontal drain

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Bob Lewis

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I thought the drain needed to be 2" up until you attached the trap fittings? Also the wall is 2x4 so can't do #2. Have another option now. Was avoiding it as the crawl space gets cramped in that area as the house sits on a little bit of a hill. Going to come up from the crawlspace with a 2" on the far right and below tie into the 3" drain line with all the appropriate elevation and cleanout considerations. The drain fitting above will be a sanitary tee and will connect the vent basically as shown in option 2. This is the only way I see of getting the sink on the right where it really should go.
 

Terry

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A sink uses a 1.5" trap and trap arm.
Drilling for the 1.5 is 2-1/8"
Drilling for a 2.0 is 2-9/16"

After the vent, then it needs to be 2"
At least that's the way my inspectors have been making me do it since the 70's
 

Bob Lewis

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So 2" can't be run horizontal through non-bearing 2x4 since max would be 2 1/4" hole (0.6 * 3.75 = 2.25).

A few more questions for you folks if you would indulge. Reading alot but haven't yet got a clear picture of how I would test my particular situation. That and my complete ignorance on the matter probably isn't helping much either. For testing I can isolate the new section of the drain below, but the vent goes upstairs connects into the upstairs master bath venting system. There wouldn't be a good way to fill with water from above so I was thinking I would do an air test and just put in test tee's above and below where the new vent attaches. Am I overcomplicating this too much and there is a much simpler way to do it?

On a side note one thing that seems curious to me is that when using test tee's and some type of ball plug the joint on the non-pressurized side of the test tee could be bad and it would never show up in the test.

laundry_room_plumbing_final.jpg
 

Bob Lewis

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I own a house that was built in the 60's from lumber that was milled on site and the 2x4 studs are 2" x 4" . I don't know where my brain is at. I was thinking actual was 1/4" less than nominal. That being the case then I don't see how drilling a 2 1/8" hole would be legal since 60% of 3.5" is 2.1".
 

Cacher_Chick

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Mathematically correct.
I think they give it that much leeway as another line in the code requires 5/8" of remaining wood on each side of the pipe.

5/8+5/8+2-1/8= 3-3/8"
 

Bob Lewis

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I guess 60% is close enough to 60.7%. Seems like times I have looked around at plumbing in open walls rarely do I see the holes exactly on center which would be required for a 2 1/8". Anyhow. Any comments/suggestions on the proper setup needed for pressure testing?
 

Bob Lewis

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Can someone throw me a bone here. Is putting a test tee on either side of where the new vent section connects reasonable? For threaded test tee's do you just put a normal plug in them once you are done? Thanks in advance for any advice you may have.
 

Cacher_Chick

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Test tees use normal cleanout plugs.

What I would do it take the drawing to your plumbing inspector and ask him what he would require for the test. Many places are doing away with the air test due to liability concerns. The pipe manufacturers no longer recommend air testing either.

When we apply for a permit, we have to supply an isometric drawing of the intended plumbing which he must approve for work to commence. That would be a good time to ask about testing.
 

Terry

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You only need one test tee at the lower end. The upper part of the test can flood out from the roof vent, or drain down the revent.
I prefer using the blow up test balls that prevent water from getting everywhere. They thread into the test tee, which when removed is replaced by the ABS threaded plug.
 

Bob Lewis

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Thanks guys. I am in the process of contacting the inspector and am hoping to go with my original option 2. A local plumber I talked to said the inspectors routinely allow 2" drain through non-bearing 2x4 walls without even using reinforcement like stud shoes. Go figure. May as well just tell you make sure a sliver of something is left on the 2x.

Three questions to your answers.

1. I was under the impression that any type of threaded fixture in a non-accessible location is prohibited. It will end up behind the dry wall. Does gluing it preclude that or would I just have the test tee facing out and open that up to be used as sort of a clean out?

2. The vent is tied into the venting system in the master bathroom upstairs bathroom so I would end up needing to plug the shower, tub, and double lav drains to get water coming out the vent stack on that side of the house? Otherwise I would be filling up the bathroom with water.

3. What is a "revent".
 

Bob Lewis

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Thought I would post an update. So many threads I come across on this forum come to an unnatural end. Talked with the inspector this morning as far as what I could do and what was needed for testing. Much simpler than I had been planning on. Looking back I had left out the fact that the vent stack serviced the toilet in the bathroom as well so option 2 wouldn't work. Back to my final design without the test tees (wahoo). Thanks for all the advice and hopefully other diy's may learn something...if you can afford it just hire a pro. I will update the post once all the rough in is done and inspected.
 
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