Adding Laundry Sink with Washer/Dryer between it and the drain

[Allen Harvey]

I'm 20%-30% of the way through remodeling our laundry room, and now I'm about ready to redo the plumbing, and like most I'm trying to minimize the work.

Attached is a picture of my exposed existing plumbing. From left to right there is a prexisting washer machine & dryer, and then to the far right will be a new cabinet with a sink in it. I'm not concerned about the water lines, just the drainage lines. The drain stack is to the far left and it vents to the roof. There's also a dryer vent in the way, but since my washer is on a pedestal, I would like to move it up some.

My current thinking is I could raise the p-trap for the laundry drain section, cutting in a new wye connector on the drain/vent stack. Then where the existing wye is, I could run it all the way to my new sink cabinet, which would be ~6.5 feet away or thereabouts. I would also have to raise the existing dryer vent box about 10 inches or so. To vent that line, I was thinking I could tee off from it and run a line up and over the existing washer drain opening. As I was drawing the attached sketch, I realized I probably can't reuse the existing wye from the washer drain because the top is 1.5" and I probably need 2" for the wye that would be stacked above it.

Is there anything I need to correct with this setup or is there a way to simplify it any more?

 

[John Gayewski]

Your drawing looks fine. You probably will, like you said, have to start over and cut the existing tee out.

You also may want to stub out of the wall for your lav a little higher than 12" from the floor. But that's up to you and your cabinet.

 

[Sponsor]

 

[wwhitney]

You have the usual issue with IPC 406.2, which requires that a washer standpipe drain be increased to 3" when it joins another drain. So your diagram does not comply with that.

The IPC does offer an alternative in 802.4.3.1, which allows a laundry standpipe and laundry sink to share a single trap. The sink has no trap, just an elbow to a horizontal waste that connects to a san-tee in the laundry standpipe before the trap. I excerpted the section below.

Cheers, Wayne

802.4.3.1 Connection of laundry tray to standpipe.

As an alternative for a laundry tray fixture connecting directly to a drainage system, a laundry tray waste line without a fixture trap shall connect to a standpipe for an automatic clothes washer drain. The standpipe shall extend not less than 30 inches (732 mm) above the weir of the standpipe trap and shall extend above the flood level rim of the laundry tray. The outlet of the laundry tray shall not be greater than 30 inches (762 mm) horizontal distance from the side of the standpipe.

 

[Allen Harvey]

Thanks for the feedback. Because there are already holes cut in some of the studs for for pipes, I want to reuse those (i.e., the run to the sink). If I have to just accept wasted holes and add new ones higher, so be it.

I don't understand the comment "a washer standpipe drain be increased to 3" when it joins another drain". What is the other drain it is joining?

In regards to the sink with the trap, I didn't draw a trap to the sink because it would be inside the cabinet and not in the wall. Does that change anything?

Thanks!

 

[Allen Harvey]

Based on 802.4.3.1 & IPC 406.2, if my sink drain line is 1.5" (I though I read somewhere it had to be 2"), can that be tied into the laundry stack (attached)? Does it need it's own vent if I do that too (i.e, connecting it the main vent by running pipe above the existing laundry stack like my original photo? Thanks!

 

[Allen Harvey]

I just realized the previous image I posted (alternate_plumbing) will not work because the horizontal distance between the sink and the laundry stack is going to be ~54 inches.

Is there any way I can hook up my sink without having to rip apart many walls in the house to change the 2" drain pipe to a 3" drain pipe?

 

[wwhitney]

I don't understand the comment "a washer standpipe drain be increased to 3" when it joins another drain". What is the other drain it is joining?

Right now, nothing, but if you add a laundry sink with its own trap, it will be joining the laundry sink, and it is supposed to be increased to 3" at point.

I just realized the previous image I posted (alternate_plumbing) will not work because the horizontal distance between the sink and the laundry stack is going to be ~54 inches.

2 things: in your drawing, there should be no trap at the sink, just an elbow (an unusual situation, think of it like a two compartment kitchen sink with one compartment being the standpipe). And the 30" limit is from the laundry sink to the standpipe, not to the stack. You can always move the standpipe closer to the sink.

And of course your other simple option is to get rid of the standpipe, just have a laundry sink plumbed as normal, and discharge the washer into the laundry sink.

Cheers, Wayne

 

[Allen Harvey]

Another thought: If the washer standpipe connects to a 2" drain (that runs through the floor), and that in turn connects to a 3" pipe, would I be ok? Would my laundry sink need to tie into the drain (that runs through the floor) above where the washer ties in, or does that not matter? Can my sink use a 1.5" pipe?

 

[wwhitney]

For a laundry sink, a 1.5" trap arm is standard. And for the IPC, the drain after the trap arm can remain 1.5".

For the laundry standpipe, a drain that carries only the laundry standpipe can be 2". Any pipe carrying the laundry standpipe drainage plus the drainage of any other fixture it is supposed to be 3" under IPC 406.2.

Cheers, Wayne

 

[Jeff H Young]

Yea IPC code not much fun in this case! on the undersized gotta have 3 inch line .
Of course cutting into stand pipe and branching that to sink might work if short enough.

 

[Allen Harvey]

Right now, nothing, but if you add a laundry sink with its own trap, it will be joining the laundry sink, and it is supposed to be increased to 3" at point.


2 things: in your drawing, there should be no trap at the sink, just an elbow (an unusual situation, think of it like a two compartment kitchen sink with one compartment being the standpipe). And the 30" limit is from the laundry sink to the standpipe, not to the stack. You can always move the standpipe closer to the sink.

And of course your other simple option is to get rid of the standpipe, just have a laundry sink plumbed as normal, and discharge the washer into the laundry sink.

Cheers, Wayne

I'm not sure how I can move the laundry standpipe to be closer to the sink since the sink and washer are at opposite ends of the wall.
I absolutely do not want the washer in any way to drain into the sink, unless I could do that all behind the wall (i.e., run a hose 50+ inches over to the sink and connect to it there). Is that allowable?

If I were to move my existing washer stack over to the right another 24" passing though another stud), is that ok? I suppose it means I would need a longer hose from my washer so that it could run behind the dryer, which is essentially where it would be located if moved.

Thank you for your help.

 

[wwhitney]

If the order on the wall has to be washer - dryer - sink, then yes the standpipe would end up behind the dryer. But depending on which side of the washer the drain hose originates, and the length of the hose, the factory hose might still reach.

Obviously opening walls to upsize the existing 2" drain to 3" is not desirable, but do you have another option for where to take the laundry sink drainage? If you can take it to an existing 3" drain, or to a 2" drain that doesn't carry the standpipe, that would work.

Cheers, Wayne

 

[Jeff H Young]

Personally plumbed hundreds of sinks and wash machines combined on 2 inch. But its legal here and works fine. its the only way I see it done.
So I hate to nit pic that you need to do it different

 

[John Gayewski]

Wait. Your putting a laundry sink into a cabinet?

I was picturing a lavatory.

 

[Reach4]

802.4.3.1 Connection of laundry tray to standpipe.

To do that, the laundry sink would need to move to the middle.


How about doing away with the standpipe, and just having a laundry sink? Then dump the washing machine drain hose above the laundry sink. That hose can be extended easily. I would tie a lint filter on the output of the washer drain hose, but others would not bother.

 

[Allen Harvey]

I think I'm now leaning towards doing what IPC 2018 802.4.3.1 shows, which admittedly is going to be a lot less work. If I move the washer standpipe to the right about 24", then I can run a simple line (no trap) to the standpipe and I'm done. No need to add in any work for venting. Only downside I can see is that the hose from the washer will need to run behind the dryer. Is there any other downside I'm missing?

Just for clarification, i'm installing a 9 inch deep sink in a standard 30" wide, 24" deep kitchen cabinet.