Can bath sink and service sink drain into 1.5" branch drain

hammerlane

I'm rethinking my garage utility sink / service sink install. I posted a question about a week ago concerning that. I'm getting mixed info concerning drainage fixture units and how many can drain into a certain size branch drain. My main question is:

Can I have a bath sink(lav) and a garage utility sink both draining into a 1.5" horizontal branch drain? A bath sink is 1 DFU and a service sink/laundry sink is 2 DFU.

Photo #1 is existing and the 1.5" I have labeled in red is showing the drain for a 1st floor bath sink that eventually ties into the 2" before the stack.

Photo #2 is looking the opposite way as photo #1.

Photo #3 is same as Photo #1 but I have placed in a 2 x 2 x 1.5 wye into the 2". The blue lines are depicting 1.5" PVC from the sink in garage.

Photo #4 is same as Photo #1 but I have placed in a 1.5 x 1.5 x 1.5 wye into the 1.5".

Would either arrangement in photo #3 or Photo #4 be OK to pick up the drainage for the garage sink?

As a note I will be using an AAV to vent the garage utility and the length of 1.5" shown in the basement photo is about 14 feet. Then there is probably another 5 feet of 1.5" in the wall to the bath sink.

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Alan

All "Sinks" require a 2" drain by UPC.

Lavatories can be 1.5"

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hammerlane

I was looking at the chart for drainage fixture units from IPC which I think Ohio is:

OK for lav sink =1 DFU and service sink/laundry sink =2 DFU
As I read 710.1(1), a 1.5" branch can have a max of 3 DFU


So there must be something that overrides the above and states that any sink other than lavatories must be 2"?

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DannyT

i would cut the 1-1/2 line to the lav out of the way and run 2 inch all the way towards the garage and pickup the lav drain with a 2x1-1/2x1-1/2 wye where it turns towards the foam in pic 2. that way you only have one line in that bay and would be much easier than trying to run another line next to the line that picks up the lav.

hammerlane

Thats a good idea and is under consideration.
Thanks for the suggestion.

hammerlane

I've looked in UPC and IPC and cannot find the specific designation for all Laundry sinks, Kitchen sinks, Service sinks..."sinks" to be 2" after the trap arm. Can you provide it?

Thanks

hammerlane

I should note that I am going to have a "laundry tray" sink in the garage...not necessarily a service sink. But "laundry tray" sink and service sink are same dfu's

ddawg16

Good timing on this thread.....I'm asking basically the same questions.......

So....what is the difference between a lavatory sink vs a bathroom sink?

I was just told this morning that I don't need a cleanout on a second floor drain.

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hammerlane

A lavatory sink is a bathroom sink. Can't answer the question on the cleanout.

BATHROOM GROUP. A group of fixtures consisting of a water closet, lavatory, bathtub or shower, including or excluding a bidet, an emergency floor drain or both. Such fixtures are located together on the same floor level.

TheEplumber

UPC table 7-3 states
Laundry sink with or without clothes washer is 2 fu
UPC table7-5 states max. 1 fu on 1.5" horizontal line
Also states in footnote 2- sinks must be on 2 " line

Lavs are not defined as sinks. Table 7-3 has a lav listed as 1 du, therefor 1.5" pipe is legal

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hammerlane

Only certain sinks like kitchen, commercial with food waste have that footnote. The laundry sink does not.

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hammerlane

here is the top half of the page from above

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ddawg16

Hammer.....just wondering....why do you use white PVC when we have to use the black ABS?

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TheEplumber

Hammer- it's true that the foot note is not there, however look at table 7-5. How many dfu's can you load on a 1.5 horizontal line? 1. Your sink is rated at 2
Codes do vary though so talk to your local authority for clarification.
As a side note, plumbers in my area rarely use 1.5" for drainage- usually just on trap arms and venting

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hammerlane

You can load 3 DFU's onto a 1.5" horizontal branch. The Lav is 1 DFU and the Laundry sink in the garage is 2. But I have about 20 feet of 2" lying around so I think we will
-cut out The majority of the existing 1.5" for the lav sink--highlighted in green in the photo below.
-the laundry sink for garage will come thru rim joist where the blue circle is in the photo--- between the two water lines which are wrapped in foam
-run all 2" to the laundry sink in the garage and the pick up the lav sink with a 2 x 2 x 1.5 wye.

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