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Old 02-01-2014, 10:36 PM   #1
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Can I drain two toilets on a 3" pipe?


I live in New York State, but not New York city. Based on my research, NY state uses the 2010 ICC code.

In the basement, I have an under slab 4" pipe that transitions into a 3" pipe. On the first floor, I will be installing a toilet and a lavatory sink. On the second floor, I want to install a toilet, lavatory sink, and shower.

My questions are as follows:

1. First, can I install two toilets on the 3" drain line? Or, must I replace the 3" with 4"?

2. I was planning on installing a double-wye connector under the toilet on the first floor, with one Y-leg heading to the second floor in 3" (for the second toilet, shower, and lavatory sink), and the second y-leg will be used for the first floor sink drain, which I will convert into 1 1/2".

3. If I do install two toilets, what size vent must I use--2" or 3"?

4. Where do I install the vent for the first floor toilet and sink? Can I put it on the second wye leg?

Thanks,
Todd

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Last edited by toddmanqa; 02-01-2014 at 10:38 PM. Reason: Meant title to say 'Can I drain two toilets on a 3" pipe'
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Old 02-02-2014, 12:02 AM   #2
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Can I drain two toilets on a 3" pipe?


2. I was planning on installing a double-wye connector under the toilet on the first floor, with one Y-leg heading to the second floor in 3" (for the second toilet, shower, and lavatory sink), and the second y-leg will be used for the first floor sink drain, which I will convert into 1 1/2".

You will need to vent both baths and you cannot do the double y because you are eliminating your wet vent on that toilet which would be the lav. A bathroom layout must always be toilet then vent then third connection in your case could you use a tee vertical on the first floor. Top going to second floor a 3 by 2 y on the first floor with 2 inch to the lav then pick up your toilet. The vent on the first floor lav should be 2 inch and tie into the second floor vents 42 inches above the floor of the second floor.

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Old 02-02-2014, 08:11 AM   #3
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Can I drain two toilets on a 3" pipe?


Is this what you meant?

http://imgur.com/Nxkj8ju
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Old 02-02-2014, 02:09 PM   #4
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Can I drain two toilets on a 3" pipe?


No thats a tee not a y fitting for the lav. You can never use a tee on its back or sideways to pick up any drainage. Only can be used in the vertical position. Like your 3 inch tee.
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Old 02-03-2014, 12:23 AM   #5
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Can I drain two toilets on a 3" pipe?


Ok. How about this?
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Old 02-03-2014, 08:22 PM   #6
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Can I drain two toilets on a 3" pipe?


Single lav only needs 1.5 inch to it.
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Old 02-03-2014, 11:24 PM   #7
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Can I drain two toilets on a 3" pipe?


how did you make those pictures?
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Old 02-04-2014, 12:21 PM   #8
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Can I drain two toilets on a 3" pipe?


Those pictures were made with Photoshop and images pulled off of Google search.
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Old 02-04-2014, 08:48 PM   #9
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Can I drain two toilets on a 3" pipe?


Your vent size will depend on distance out the roof. > 40' 2 inch

Otherwise 1.5 inch.
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Old 02-04-2014, 10:23 PM   #10
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Can I drain two toilets on a 3" pipe?


post a rough shop drawing if i am thinking, what your wanting to do its not correct.. venting and sanitary must be kept independent on each floor.

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