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Adding laundry sink to washer drain

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snrusnak

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Hi, I'm adding a laundry sink to a washer drain, and want to make sure I do it properly and vent it properly. The new sink will have a P-trap under it and come in from the left in the picture. Is it acceptable to tie in a new TEE above the existing TEE where the washer drain ties in? I believe the washer drain is 2" and the vent pipe above the existing TEE is 1.5". If this is not acceptable, what is the proper way to do this? Thank you in advance!
 

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frodo

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hey gulfport?

if it was me, I would approach it a different way if possible
Matts way is not wrong, my way is just different
washer drain pumps are powerful, a cross would let the pumped water to go straight through to the sink
 

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snrusnak

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Yessir, Gulfport. Was nice and cool out this morning!!!

I understand your concern about the cross flow from the washer pump, but am not following your drawing. I'm going to get some sleep and will look at it again tomorrow lol!
 

Zanne

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I think Frodo is suggesting that you tie in the sink's trap arm above the washing machine's drain instead of tying them in at the same level. I could be mistaken though. My brain is not operating at full capacity right now.
 

snrusnak

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So we had a hurricane come through then we went on vacation for a week, so I'm delayed responding back. I appreciate all the input. I probably failed to mention, but this job is going to take place in Florida, not in MS where I live. I'll be helping my dad install this in his house over christmas. So, I thought it was (maybe?) not acceptable or proper to tie in the sink trap arm above the washing machine drain (speaking to Frodo's picture), due to venting issues? Can I get some more help/clarification? This would actually be easier to do in this situation.
 

Zanne

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Sorry to hear about the hurricanes. I'm in Louisiana and my area got hit with 2 hurricanes within something like 45 days & it sucked. One of the concerns with the washing machine and sink sharing a drain & vent is that washing machines can have suds backflow. It also uses very large quantities of water with greater force so it can siphon water out of the sink's P-trap.

You never want to tie in the washer upstream of other fixtures (unless you want a chance of suds coming up into them). So you would want to tie your washing machine's trap arm in below the sink's trap arm. If I'm interpreting Frodo's drawing correctly, he's saying to have 1.5" vent above the cleanout for the vent shared by sink & standpipe. Piping for the sink will be 1.5" but merge with a 2" pipe (which is minimum required size for a washing machine drain).

Do I have that right, @frodo?
 

snrusnak

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Thank you for the reply. So I understand your drawing, what I'm confused about is that I thought it wasn't proper to connect this way. Something to do with not having a common venting when drain arms tie together at different elevations? Like if the sink arm is draining it will block the vent for the washer? Maybe I'm totally wrong I just thought I had seen this when I was trying to research how to tie this together, which is why I came to the forum with the question. I tried to circle the area in green that I'm talking about.
 

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Zanne

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So long as the sink doesn't have too much water draining at the same time the washing machine is draining it shouldn't be a problem. So, don't fill the sink and let it drain while the washing machine is draining. You can wait until the washing machine has drained or drain the sink while the washing machine is filling.
Whichever one you have on top will likely block the vent for the other, but the washing machine has higher volume of water coming out so it is more likely to block the vent than the sink is. Not only does it contain more water, it is a larger pipe size & has more force behind the draining than the sink will. Having individual vents is ideal, but if you're going to wet vent, it's best to have the sink's drain above the washing machine's.
laundrysinkstandpipediag.jpg
 

snrusnak

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I see, thanks for the explanation. Looking back at my pictures of what I'm working on, I don't know that I have the space to achieve what you've sketched. I'll have to ponder on this for a bit and figure out what to do...
 
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