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Can sewer vent pipes have 90-degree bends?

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Angelique

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We're rebuilding a bathroom from scratch. The plumbers had to reroute the sink vent pipe. It used to be mostly straight, with one 45-degree bend. Now it has two 90-degree bends. I've attached a photo of one of them.

Is this okay? We've had problems with sewer gas before, and I don't want to have that problem again.

2014 06 27 sink vent pipes 01.jpg
 

johnjh2o

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Assuming the waste line is 18" off the floor the length of the riser above the tee would need to be 24". I'm not seeing that.
 

Angelique

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Thanks for the replies. It is definitely way too low for the standard you are talking about. I alerted the contractor, and the plumber just happened to call about scheduling so I talked to him about it. He says that according to Arizona code, you don't have to have to be 6" above the sink flood plain if the sink is the only thing using that vent pipe.

Nevertheless, I'm wondering if we should have him change it to 45 degrees. (We can't raise the 90 degree turn because of the new medicine cabinet.)
 

Matt30

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Well....then i guess im just a horrible judge of distance :eek:

Whats moving thru those pipes is just air pressure and gasses. As long as those pipes are running level or slightly graded back towards the fixture, you will have no issues. Its not rocket science.
 

johnjh2o

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The reasoning behind not running a vent horizontal below the flood rim is if the waste line should become plugged the vent line could fill with debris clogging the vent and remaining after the line is cleared.
 

Zanne

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I'm not an expert, but I'm going to call BS on the Arizona code not calling for the 6" above flood level.

According to what I looked up and posted here, Arizona uses UPC at state level and can use IPC at local levels. I think that both of those have the 6" requirement (someone please correct me if I'm mistaken). I think that your plumber is either wrong or just doesn't want to fix it and is lying to you. I think you should get a second opinion. Perhaps you can contact someone from your local Dept of Health and Sanitation and ask them about it. If your plumber is lying to you, then I suggest you report that to the Dept of Health so they know about it and can take him to task. If it turns out he's being truthful, then I don't know what to tell you.
 

Angelique

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Arizona uses UPC at state level and can use IPC at local levels. I think that both of those have the 6" requirement.
The plumber said that Arizona has the 6" requirement if more than one fixture (such as two sinks) are sharing a pipe. The requirement does not apply to single sinks. Are you doubting this exception to the requirement?
 

johnjh2o

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The plumber said that Arizona has the 6" requirement if more than one fixture (such as two sinks) are sharing a pipe. The requirement does not apply to single sinks. Are you doubting this exception to the requirement?
That explanation makes no sense to me.
 

Zanne

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The plumber said that Arizona has the 6" requirement if more than one fixture (such as two sinks) are sharing a pipe. The requirement does not apply to single sinks. Are you doubting this exception to the requirement?
Yes. I have never heard of such an exception, and while I am not a plumber or an expert, the statement your plumber made does not make any sense. As others have already stated, the point of having the 6" vertical run above is not only about flooding other fixtures, its about maintaining balance if/when the fixture becomes filled to its flood level and there is a clog preventing water from flowing down.

From what I understand, if the horizontal run starts below the flood level, then the water can go in to the horizontal part and possibly carry debris and clog the vent. If water goes up a vertical run, it can drop back down again via gravity, but in a horizontal run stuff can get stuck more easily. The vent line, unlike the waste line, generally does not have water flowing down in to it to clear it out so debris in a horizontal line is unlikely to be washed away (unless you specifically spray something down to clear it). The number of fixtures hooked to it does not change the fact that the premature horizontal line can become clogged. Additionally, when the vent is clogged, the air pressure cannot be equalized and it can make things worse. Water will take the path of least resistance-- and with an open basin, the least resistance will be out over the flood level of the sink and on to the floor.

Here is a crappy rough sketch to illustrate based on my understanding. If I am incorrect, someone please let me know.
 
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Jamesplumbing06

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I dunno I see the codes and abide them but this one has gotten me. If the pipe is clogged then the pipe is clogged. Cram 20- elbows together or have a straight pipe it’s still clogged. And if drain is clogged. Then vent is restricted. I think it’s got something to do with atmospheric pressure. The elbow creates a small restriction to bend air. If it’s close to same level as trap water then it could pull on trap water while trying to break the restriction of elbow. But if elbow is higher than trap water. Maybe the suction has already passed trap and weakened as it climbs higher to elbow. Has more air volum to take up before it can pull on trap. But yeah everyone goes to the clog explanation. So I stay confused and just go by code which is 6” above flood rim here. No exceptions.
 

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