Adding washing machine drain to copper drain under kitchen sink

[Jeff H Young]

No No, not my recommendation at all Option B "possibly move tub tee with no trap" with the illustration you posted.
Actualy option b seems to have 2 options to it? horizontaly wet venting the washing machine isnt my idea

 

[Tooltalk]

No No, no9t my recomendation at all Option B "possibly move tub tee with no trap" with the illustration you posted.
Actualy option b seems to have 2 options to it? horizontaly wet venting the washing machine isnt my idea

Sorry if I misunderstood and yes I confused matters by adding third option of moving the tub tee to stand pipe. If we call that option C, which option are you recommending? Sounds like you're saying inserting the tub tee or wye into the trap arm creates a wet vent for the washing machine. Isn't the same thing happening in option A (my original drawing) that Terry and others said was OK?

 

[Sponsor]

 

[Tooltalk]

Ok, let's try this again. Think I'm starting to understand wet venting and I'd prefer not to connect laundry tub to standpipe, since I may replace tub with different sink in future. Thanks for everyone's patience while I work this.

 

[John Gayewski]

The problem I see is that your using an AAV and have water falling from the floor above. Meaning the air has to be displaced somewhere. I do think it's better to have them drain into the stack separately, but it's possible there will be no problem. At least draining them into the stack separately creates a large area for the air to travel through.

 

[WorthFlorida]

Thank you for your follow ups and questions. All are well thought out looking for solutions.

I have to agree with John Gayewski. AAV's are a one way check valve, they only allow air into the pipe as water travels down the pipe sucking air. In front of the water slug air is being pushed and it needs to go somewhere. What could happen on your last configuration is as water comes down from the kitchen sink, the air will try to escape through the washer trap. You'll probably hear gurgling or bubbling coming out of the washer standpipe if the pressure cannot be relieved adequately through the roof vent.
Most likely you will be OK. My home built in 2007 has one roof vent and AAV's just everywhere except where the washer is located. The kitchen, near the washer and all bathroom sinks, second floor bathroom have AAV's. One AAV handles the second floor bathroom, two sinks, toilet and bathtub. Zero issues with drainage.

What is unknown is where is the main stack from this drain and the whole house roof vent?

From Studor AAV specifications: (having to be above flood stage for a sink is usually not possible, therefore it recommends it be 4" above the trap arm).
1) Studor AAVs must be located a minimum of four (4”) inches above the horizontal branch drain or fixture drain being vented.
2) A minimum of one vent pipe shall extended to the open atmosphere for each building drainage system for relief of positive pressure, the size of this vent is not specified because this single vent does not determine the total amount of aggregate cross-sectional area of the vent system.

 

[Tooltalk]

What could happen on your last configuration is as water comes down from the kitchen sink, the air will try to escape through the washer trap. You'll probably hear gurgling or bubbling coming out of the washer standpipe if the pressure cannot be relieved adequately through the roof vent.
Most likely you will be OK.

What is unknown is where is the main stack from this drain and the whole house roof vent?

Thanks for your response and explanation. That helps me better understand the potential problems. The only main stack is at the back of the house where the main floor bathroom is. The kitchen sink is at the front of the house about 30-40 feet from the stack. It is a story and half house, with knee walls and bedrooms upstairs, and attic spaces on either side. So might be difficult to run pipe to extend vent to front of house. Would be easier to add roof vent in attic space above kitchen, but there is a window over the kitchen sink, so no easy way to get a vent pipe up to the attic without some demo work and renovations that seem like overkill for a situation like this. That's why I was going to add an AAV under the sink and one in basement for laundry.

Our kitchen sink has had been unvented and gurgling since our family move here in the 60s. So if some gurgling in the washer stand pipe is the worst case scenario, I think I can live with that.

Our current laundry drain that we've been using for decades also goes into an 1.5" s-trap. So I think any of the options I've described should be a big improvement.

 

[Tooltalk]

No turning back now. The old cast iron came out easier than I expected. I was surprised there was no lead in the joint at all. It seemed like oakum mixed with something like cement on top, then oily, greasy oakum below that.

I'm starting with kitchen sink side this morning and will tackle laundry side later. So I'm still open to any advice about connecting and venting the laundry sink, since that seems to be causing most of the concern.

 

[Tooltalk]

You could use a santee first and head over to the washer. It will need to be vented with the AAV.
The upstairs kitchen can drop into the top of the santee as long as there is a vent on the trap arm.

Hi Terry. Sorry if I'm asking the same question over and over, but is this what you were describing with the vent on the trap arm? In one of my previous images I had the vent in front of the wye for the laundry tub.

I'm just about ready to start gluing things up, so I'd really appreciate some confirmation that I have trap arm vent in right place.

Thanks.

 

[Terry]

The laundry tub and the washer need their own vents. You can take the two vents and tie them back together above the flood level.

Or something like below.

 

[Tooltalk]

The laundry tub and the washer need their own vents. You can take the two vents and tie them back together above the flood level.

Thanks for quick reply. So was this one I posted the other day correct?

 

[Reach4]

Your vent vents the standpipe, but on the codes we are familiar with, the trap for the laundry tub needs to be vented before joining the vented standpipe drainage. So two trap, two vents.

The people who post here regularly are not that familiar with Ontario codes. I know there are differences, but this would not be a difference I have read of.

One of the US codes, IPC, allows the laundry sink to drain, without its own trap, to the upstream side of the standpipe with some limitations. I don't know that Ontario would be good with that.

I suspect that what you propose would work great, but not be within code.

 

[Tooltalk]

Your vent vents the standpipe, but on the codes we are familiar with, the trap for the laundry tub needs to be vented before joining the vented standpipe drainage. So two trap, two vents.

I think we were posting at same time. Did you see my most recent image. It has two vent pipes that tie back together above the flood level, as Terry suggested.

Thanks.

 

[Reach4]

Venting of a trap arm should occur before that waste joins other waste. So your drawing does not address that.

You might be able to use vertical wet venting with the trap arm for the sink above the trap arm for the laundry. But again, I don't know what Ontario thinks of that. The sink will not want its trap too low due to the restricted height of the bottom of the sink.

Post people think the little cleanout on the bottom of your trap to be pointless.

One thing that would work is a 2-inch double fixture fitting, with the AAV on the inlet. I think you can get a trap adapter that goes into a 2 inch hub, but accepts a 1.5 inch slip joint trap arm. The problem that some have with that is the ease of snaking, but if you unscrew the AAV, you have a great snake inlet.

 

[Tooltalk]

Venting of a trap arm should occur before that waste joins other waste. So your drawing does not address that.

You might be able to use vertical wet venting with the trap arm for the sink above the trap arm for the laundry. But again, I don't know what Ontario thinks of that. The sink will not want its trap too low.

Post people think the little cleanout on the bottom of your trap to be pointless.

Thanks for helping. I think I finally understand what you're saying about the vents. Not sure I have room to add a vent to the sink trap arm before it joins the trap arm for the washer, but I'll play around with some fittings and see. I'm pretty sure Ontario does allow the sink to connect to washer stand pipe above p-trap. I tried that, but couldn't make it work. Sinks sits too low and washer trap arm too high. I think we can also connect stand pipe above sink p-trap, but I couldn't make that work either.

Easiest solution would to abandon the washer stand pipe and just dump washer into sink, but it's kind of bugging me that I can't figure this out.

 

[Reach4]

So route sink trap arm to a trap adapter in a combo (or a sanitary tee on its back, as allowed by IPC for venting). AAV pipe connects to side port. That can be a separate AAV or you can tee off the AAV path higher than the flood level of the standpipe and the sink. Run the output of that fitting horizontally to join the vented standpipe drainage.

Also, after the sink has been separately vented, you can join the kitchen waste if you prefer.

 

[Tooltalk]

So route sink trap arm to a trap adapter in a combo (or a sanitary tee on its back, as allowed by IPC for venting). AAV pipe connects to side port. That can be a separate AAV or you can tee off the AAV path higher than the flood level of the standpipe and the sink. Run the output of that fitting horizontally to join the vented standpipe drainage.

Also, after the sink has been separately vented, you can join the kitchen waste if you prefer.

Having a bit of trouble visualizing all that and I'm not familiar with all the plumbing lingo. What's a combo?

Edit, just Googled it and see it's combination Wye & 1/8 bend already made in one fitting. I guess that saves some space. Out shopping now and 'll see if I can find one.

 

[Reach4]

Combo does not save space vs a wye and a street 45. Compared to a sanitary tee, it is huge. Some codes don't allow a pipe to be vented with a santee using the middle port as a vent. Everybody accepts a combo or a 45+wye for that.

 

[Tooltalk]

So route sink trap arm to a trap adapter in a combo (or a sanitary tee on its back, as allowed by IPC for venting). AAV pipe connects to side port. That can be a separate AAV or you can tee off the AAV path higher than the flood level of the standpipe and the sink. Run the output of that fitting horizontally to join the vented standpipe drainage.

Also, after the sink has been separately vented, you can join the kitchen waste if you prefer.

Am I getting closer?

If this setup works, does the pipe between washer p-trap and washer vent wye need to be at least 4 inches, or is the wye considered part of the trap arm? Edit: found the answer to this in image below.

 

[Reach4]

Closer, but make the laundry sink vent be two 45s instead of a 90.

45 degrees off of plumb is considered vertical, tho the AAV needs to be within I think it is 15 degrees of plumb.

 

[Tooltalk]

Closer, but make the laundry sink vent be two 45s instead of a 90.

45 degrees off of plumb is considered vertical, tho the AAV needs to be within I think it is 15 degrees of plumb.

I wondered about that. I didn't have any 1.5" 45s handy, but will get a couple tomorrow. Also, with the current height of the laundry branch the 45 degree vent wouldn't clear bottom of sink. If I remove the kitchen wye on top of the cleanout from under laundry tee, I can lower the laundry branch to provide more room for the 45s to clear bottom of sink. Once all the pieces are glued, the vent tee should be a bit closer to wall too. So that will help as well.

Thank you very much for finally making this clear to me!