Best Option for Laundry Drain Tie In?

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bshmstr

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I am in the process of adding a washer and dryer on the second floor of my two story home. They will be located on the other side of the wall from a bathroom group (tub/shower, toilet, and lavatory) so I have relatively good access for routing the drains and supply lines. My question is what is the easiest way to tie into the existing drains while remaining code compliant? The house was built in 2000 and the code adopted by my jurisdiction is the 2015 IPC.


I have attached a sketch that shows the existing DWV, which is comprised of schedule 40 PVC. I will be running the a 2” drain for the laundry and have the ability to tie into the existing vent system (with either 1.5” or 2” pipe) at the location of the new waste and vent system being added for the laundry. There is a 3” wye fitting with a street 45 fitting connecting to the vertical waste and and vent stack going into the attic, and this is what (I think) comprises the wet vent for the tub and toilet. One side of the wye fitting has a 3” to 1.5” reducer bushing that is connecting to the tub’s trap and thus comprising the trap arm for the tub. On the other side of the wye, the wet vent and waste continues in 3” pipe where it catches the toilet (WC) before heading down the stack drain stack to the basement. I’m thinking that the easiest way to tie in will be to redo the existing transition from the 1.5” tub drain to the 3” waste and vent. I’ve also included a picture of the fitting in question for reference.


I’d like to avoid redoing the entire wye fitting, so I’m thinking I can remove the reducer bushing and replace it with 3” pipe that extends 1 or 2 joist bays to the left (upstream). From there I can use a fitting such as 3” x 3” x 2”Comb Wye & 1/8 bend (link below) to tie in the laundry drain to the 3” line in conjunction with a new 3” to 1.5 reducing bushing to connect back to the tub drain. Is this a valid option? I think I’m getting tripped up about whether or not there are any code compliance issues in the IPC with regards to tying into the trap arm for the tub? I guess if I were to do this the tub would technically become wet vented via the 2” laundry drain? Please let me know if there is an easier way to do this or if there are any errors in my plan as proposed. Thanks in advance!

DWV Layout.jpeg
Tie In Location.jpeg


https://www.homedepot.com/p/Charlot...Wye-and-1-8-lbs-Bend-PVC005021400HD/203396246
 

Reach4

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think I’m getting tripped up about whether or not there are any code compliance issues in the IPC with regards to tying into the trap arm for the tub? I guess if I were to do this the tub would technically become wet vented via the 2” laundry drain? Please let me know if there is an easier way to do this or if there are any errors in my plan as proposed.
That is a no-go. What you can do is to tie the new laundry standpipe downstream of all of the bathroom stuff.
 

bshmstr

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That is a no-go. What you can do is to tie the new laundry standpipe downstream of all of the bathroom stuff.

Thank you Reach! I'll poke some more holes in the ceiling and look for a place to tie in downstream of the bathroom, but there should be sufficient space to do that. Can you help me understand the reason why my initial plan won't work for future reference?
 

Reach4

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Here are some rules:
1. In IPC, a laundry standpipe can only join other waste in a 3-inch or bigger pipe.
2. A not-bathroom drain, such as a laundry standpipe, will interrupt bathroom wet venting. So if you inject the standpipe upstream of the toilet, that toilet would have to have its own vent, rather than relying on the wet venting from the lavatory.
 

bshmstr

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Here are some rules:
1. In IPC, a laundry standpipe can only join other waste in a 3-inch or bigger pipe.
2. A not-bathroom drain, such as a laundry standpipe, will interrupt bathroom wet venting. So if you inject the standpipe upstream of the toilet, that toilet would have to have its own vent, rather than relying on the wet venting from the lavatory.

I'm following the second point, which does not allow for the connection I initially proposed, but I'm not tracking on the first. If I stepped the standpipe up to 3 inches before joining it to the 3" pipe with something like a 3” x 3” x 3”Comb Wye & 1/8 bend (link below) would that work? Do I need to use such a fitting when tying in downstream of the bathroom group or would the initially proposed 3” x 3” x 2”Comb Wye & 1/8 bend be appropriate?

https://www.homedepot.com/p/Charlot...omb-Wye-and-1-8-Bend-PVC005011000HD/203396239
 

wwhitney

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3x3x2 is fine. The point is that the IPC prohibits a 2" laundry standpipe drain from joining, say, a 2" kitchen drain via a 2" wye or combo. Any drain carrying the laundry standpipe and at least one other fixture has to be at least 3".

Cheers, Wayne
 
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