Vent reducer in horizontal position?

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krik

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Does code allow a 3" to 2" reducer to be used horizontally in a vent system? Water couldn't totally drain back to the fixtures because of it, so I have a feeling it's may not be correct. But I just want to check because a workaround is going to be complicated.
 

krik

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A vent is the one place you can reduce in the direction of flow, but it has to be done vertically for the very reason you describe.

so if I need to have a reduction in a horizontal run, how would I go about that? this is a 3" roof vent that has to turn horizontal due to an irreplaceable vertical pipe being abandoned, and I have to run horizontal for 25 ft where I can't fit 3" pipe - both need to run at the same height (otherwise I'd just run the 2" lower), so would something like this work - side view (bear with me on the lousy graphics):

vent..jpg
 

Reach4

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I wonder how the PVC Pipe Fitting, Eccentric Reducer Coupling, Speers 3729-338E or equiv would be viewed.
429-338e-eccentric-reducer-coupling_1.jpg
 

krik

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Alternatively, may I use a regular reducer if it comes off a 3x3x3 or 3x3x2 tee with the tee leg going down for drainage? I do have the reducer right after a set of tees, so it's not just in the middle of a horizontal run with nowhere to tie in.
 

hj

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Try to find an eccentric reducer when you need one. Your 2" cannot drop down and then connect to the 3". You need a "heel inlet 1/4 bend", 3x2x3, so the 2" goes right in to it.
 

krik

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Try to find an eccentric reducer when you need one. Your 2" cannot drop down and then connect to the 3". You need a "heel inlet 1/4 bend", 3x2x3, so the 2" goes right in to it.

Got it - low heel inlet OK? Those are in stock at the local big box home improvement store. And I can put a 3x2 reducer on the downward leg of the heel inlet then, right?

I thought I might be able to put the 3x2 reducer horizontal on a 3x3x2 tee because it would drain directly into the vertical 2" leg when it's not pitched. But I don't want to risk getting it rejected if that's too far from any common practice / sense.
 

krik

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BTW - perhaps a silly question, but why couldn't you have a drop in venting if it's connected to a vertical? Air doesn't care much if it moves up or down, and it would drain just fine. Same would go for a horizontal run between two verticals that arches upwards with the highest point in the middle?
 

hj

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Now, you are trying to be logical, and inspectors are not always logical. They go by what the code says, and the code says the vents should ALWAYS go upwards. I have even have them reject a fitting where the "flow" is the wrong way, even though air doesn't care which way the flow should be.
 

krik

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Now, you are trying to be logical, and inspectors are not always logical. They go by what the code says, and the code says the vents should ALWAYS go upwards. I have even have them reject a fitting where the "flow" is the wrong way, even though air doesn't care which way the flow should be.

Upwards from ... the fixture it serves? towards the roof vent?

The interpretation of code language here actually confuses me when it says "to allow moisture and condensate to drain back to the soil or waste pipe by gravity" (IPC?) and "graded and connected as to drain back to the drainage pipe by gravity" (UPC 905.2) ---- it says nothing about _which_ pipe that is, but some materials claim it needs to drain to the fixture it serves. However, this publication from Plumbing Assoc of GA says on the section 905 slide it can go up or down (http://www.plumbingpros.com/pdf/dwvents.pdf) which makes more sense given how 905.2 is worded.

I guess it's up to the inspector whether upward venting would be rejected? To play it safe I'll go down only, even though it makes for some complications.
 
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BMWpowere36m3

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The only one that goes up and down is the island vent loop... which I think is a special case. If the vent pipe goes up and down, condensate can collect at the lowest point. It's supposed to be able to drain back to the waste line.
 
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