Water and sewage air backing up the washer pipe

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Qwertyjjj

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The picture attached is of the 2nd floor plumbing in a 3 floor building.
Today I was using the sink here on the 2nd floor and the upstairs apartment either flushed their toilet or also used some kitchen water. At the exact same time a load of water splurted out the washer drain pipe and then a load of sewage air.
This sounds like a venting problem, maybe it doesn't happen normally as the sink could unintentionally be used as a air vent in this pipe setup. But the water backing up is odd.
Any ideas what could cause that and how to fix?
20171121_142053.jpg
 

Reach4

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That plumbing in the picture was never right. There is no vent for the standpipe. There is probably no vent for the sink, although maybe there is an AAV not shown.

I would think there is probably a partial drain blockage, although I cannot be sure there is not a vent problem contributing.

Are you the tenant or the landlord?
 

Qwertyjjj

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20171121_145523.jpg
That plumbing in the picture was never right. There is no vent for the standpipe. There is probably no vent for the sink, although maybe there is an AAV not shown.

I would think there is probably a partial drain blockage, although I cannot be sure there is not a vent problem contributing.

Are you the tenant or the landlord?
Landlord. I'm wondering whether to put an AAV in and if that would fix it. But what causes the water to rush up the standpipe? If it was a venting issue, wouldn't the sink gurgle for air?
Sink has p trap and no vent.
 
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Terry

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Both the washer and the sink need venting. The way it is now, you need two vents. With the washer dumping over the sink, that's going to be an issue.
For gurgling to happen, there has to be some water left in the trap. It most likely is being sucked out.
And of course, it could be a slow drain too. Normally a washer is plumbed with 2", not 1.5"
2" pipe is twice the area of 1-1/2"
 

Qwertyjjj

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Not sure how far down the 1.5" drain goes. So, try an AAV after the p trap in sink and another AAV on the left side of all these pipes?
Wouldn't one AAV in the horizontal pipe do the job?
Isn;t it more likely a blocked drain further down?
 
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I don't think an aav is going to help you here, if the splurt and gurgle is coming from positive pressure of a slug of water from upstairs. Aav only relieves vacuum, not pressure. I think you need a full vent out the roof or a revent above the 3rd floor to completely fix this.
 

Qwertyjjj

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Why would there be positive pressure? Let's say the sink upstairs shared the same down pipe to the basement. Wouldn't waste water just stop flowing until the other had finished and then flow further? Even if a vent was added to the roof, the air vent is not supposed to have water from a postive air flow pushing liquid up it?
 

Jadnashua

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IF the pipe were full of water, the water column would provide 0.43#/foot of elevation. Then, assuming the waste is flowing, you've got gravity trying to accelerate it. Positive pressure isn't hard to achieve...it won't be huge, but it doesn't need to be to create a potential problem when things aren't done properly.
 

Qwertyjjj

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IF the pipe were full of water, the water column would provide 0.43#/foot of elevation. Then, assuming the waste is flowing, you've got gravity trying to accelerate it. Positive pressure isn't hard to achieve...it won't be huge, but it doesn't need to be to create a potential problem when things aren't done properly.
Yes but for the pipe to be full of water, it would have to be full through all 3 floors of the building down to the basement where it hits the 4" waste pipe.
Water would be coming out of drain holes on the first floor and they're not, unless nothing's shared with that pipe of course.
Either way though, adding a vent in this pipe doesn't stop it becoming full?
 

Jadnashua

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A slug of waste falling down a drain can try to push air ahead of it, and suck air in from behind. A proper venting system breaks that siphon and you need it to be right at each trap along the way.
 
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