How to drain/vent vanity & washing machine together (pics)..?

[thatotherguy]

I've searched a million articles and haven't come up with a solid answer to this...

I'm converting the previous owners' bathroom addition into a bathroom/laundry room. I need to run the sink and washing machine into same drain/vent but from opposite sides. I've attached two pics. All lines are 2" pvc.

1) Which pic is correct/adequate (the second has dotted lines where I maybe can add another cheater vent, if that's what it's called)?

2) And do I need to use 3" pvc, starting where the washing machine and vanity drains combine?

Because of various obstacles, there can only be this one drain, in this one place. The right end heads through a wall and into the vanity cabinet through the side. (Literally, the right end in the pic is the left side of the vanity cabinet.) I'll plumb the sink drain/trap in standard 1.5" and then transition into the 2" line at that wall.

Thanks for the help.

 

[Stuff]

You want something like this but reversed. Notice stacked san-t's with washer standpipe connected on bottom.

 

[Sponsor]

 

[thatotherguy]

You mean to stack the combo tee-wyes? I saw that pic before. But they didn' use a 4-way in your pic, because the lines weren't coming from opposite sides, don't you think? Wouldn't a 4-way be better in this case?

 

[Stuff]

Those are stacked san-tees vertically in the picture, not combo as a combo on top would not vent the sink properly. Bottom OK to be combo since is for drain only. The combo on its back for the washer is a different story. A san-tee on its back is a normally a no-no though should be okay as for vent.

A 4-way double wye can't be used for venting. A 4-way double fixture fitting can work but not recommended. https://terrylove.com/forums/index.php?threads/why-cant-a-double-sanitary-tee-be-used-here.49386/

 

[Terry]

On my picture, the washer comes in below the sink. The sink has it's own vent.
The washer also has it's own vent, a combo because in the UPC code they are not allowing a santee on it's back there.

Codes change over the years and what I did in the 70's is not the same as in 2000 and beyond.

 

[thatotherguy]

Okay, so I'll add the vent for the washer (dotted lines, joined with a combo on its back), and take out the middle vent, as it doesn't serve a purpose. Both lines will be vented. Then will stack tees for washer and dryer.

1. I connect to the horizontal main drain line (3" PVC, in crawlspace) with a combo though, right?

2. With all the talk about tees and combos, I realized that my toilet drain column uses a combo to vent. Is it a huge problem?

 

[Terry]

2. With all the talk about tees and combos, I realized that my toilet drain column uses a combo to vent. Is it a huge problem?

The toilet unlike all of the other fixtures is supposed to siphon. The bowl then gets refilled from the tank and fill valve.
The vent with the combo or wye is fine, however it's best to keep it at a 45 or vertical and have no horizontal to it unless it's being wet vented by something like a lav. A flat vent without the ability to snake it clear can clog at some point.

 

[thatotherguy]

That's a relief. So you're saying that it would have been best to keep the vent at 45 degrees, but a wye does that, though. So the combo is okay, but the wye or tee is better, right? Or only a wye is best? Just making sure I understand