Do waste vents pipes have to slope towards the fixture?

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  #1  
Old 11-20-16, 04:54 PM
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Do waste vents pipes have to slope towards the fixture?

I have a grand idea to put up some shelving in my walk up attic area. A minor annoyance in my plan is the presence of a waste vent pipe from the 1st floor laundry room that runs through this area. I'd like to relocate it if it's not too much trouble. The shelves will go up either way.
The red marks on the pics show the height of the pipe above floor level to indicate slope in the existing pipe and the termination points of the pipes. The green lines show how I'd like to reroute the pipe, but I'm pretty sure I can't do this. I would essentially be creating a de facto trap if I increase the height of the pipe and then slope away from the fixture before turning up again to rise vertically through the roof.

I'm not a plumber though. I'm an engineer and a DIYer. So tell me wise ones...can I do what I want to do? Do you have other ideas to accomplish the same thing?
 
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  #2  
Old 11-20-16, 05:05 PM
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Can't you just continue the vent pipe straight up from the floor to have it exit closer to the ridge instead of having it take that horizontal detour to exit through the roof near the eave ?
 
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Old 11-20-16, 05:10 PM
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To answer your question, yes vent pipes must slope to the drain. If they don't slope toward the drain and they fill with water from rain or condensation, they aren't venting anymore, now, are they?

Your vent should go straight up through the roof in a new location.
 
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Old 11-20-16, 05:18 PM
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I would say you need a new hole in the roof as Vermont suggested.

Another option is an air admittance valve. You will have to check local plumbing code to see if they're allowed.
I have an AAV in my laundry and they work fine and should be approved in most areas.
The valve eliminates the need for a vent pipe and must be installed properly to meet code.
 
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Old 11-20-16, 06:09 PM
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Not really sure why, but the pipe is ~18" above floor level before the first elbow and vertical portion of the run. Perhaps I can go back to the point where it protrudes through the ceiling, put an elbow there to run it horizontal (sloped 1/4" per foot) under the attic floor, then another elbow to turn it up and through the existing hole.
 
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Old 11-21-16, 04:52 AM
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Keep in mind that the attic is just empty space not intended for anything. So, plumbers put things where it's convenient and easy to install. Why bend down all the way to the floor if knee high is easier?

Relocating the vent to penetrate the roof right above the bath is one idea. Vents are often relocated like yours so they are not visible. When you're out driving around notice that most houses do not have visible vents. They penetrate on the back side of the roof and far enough down that the vent pipe is not visible above the ridge of the roof. There is nothing wrong with moving yours but you might be able to see it.
 
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Old 11-21-16, 04:55 AM
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Personally a vent pipe you can see from the street doesn't bother me any. I have painted for builders that would have us paint the vent pipes the same color as the roof to make them less visible.
 
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Old 11-22-16, 06:32 AM
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OP here: I've already asked one stupid question, so I have no reputation to be concerned with...so I'll ask another one.

Why must the vent go through the roof to outside? The attic itself is vented. Why can't the vent pipe just come straight up from the drain line into the attic area. Seems like as long as it's above the insulation level, mother nature would never care.
 
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Old 11-22-16, 06:55 AM
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As a Real Estate Broker, I've seen many houses that have survived decades (or over 100 years) being vented into the attic; but moisture condenses on the 1st cold surface it encounters, and sometimes that creates brown icicles. And sometimes the attic had an obvious odor of sewage . . . . making it one of the least marketable aspects of the property.

I'd always opt to go outdoors; but that Air Admittance Valve HandyOne suggested might be a good temporary option. I say "temporary" because I've also been in dwellings where the flapper on the AAV fatigued and the dwelling was loaded up with explosive and noxious methane which also carries certain deleterious bacteria.
 
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Old 11-27-16, 06:50 PM
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You can't directly vent it in the attic. There are potentially sewer gasses that you definitely don't want in your living space.

Since you most likely have a main stack vent (a 3" or 4" vent somewhere else through the roof), as others have said you may be able to use an AAV. An AAV (or Studor vent) allows the vent to pressure-balance, without allowing those pesky sewer gasses from getting out. They work great, but aren't allowed everywhere and have a tendency to fail after a while. That's why if at all possible, you really want to get the vent up and out the roof.
 
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Old 11-29-16, 06:51 AM
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OP here again with an update: the house is only a year old. I really have no interest in cutting a new hole in the roof to relocate the vent. If I'd noticed it and thought about it during contruction, I would've asked them to redo it, but what's done is done. It won't stop the shelving project, but it will create an obstacle to work around.

As for rerouting the pipe - no can do. The pipe comes straight up into the attic 2 feet or so above the floor level before taking a horizontal turn. Upon further investigation, I can tell you the reason for that is the raised ceiling downstairs/raised attic floor level in a localized area. The reason for that protrusion in the second picture I posted is the stairway that comes upstairs. It makes more sense now.

Thanks to everyone for your advice. I'll have more questions in a different thread related to a bathroom I'm installing.
 
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Old 11-29-16, 12:20 PM
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So . . . . how are you opting to solve your impasse ?
 
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Old 11-29-16, 08:18 PM
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@Vermont, it sounds like the OP is just going to leave the pipe as-is and install shelves around it. Sometimes easier is better

Take and post some pics once it's done - would love to see the finished product!
 
  #14  
Old 11-30-16, 11:45 PM
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I'd look into poking it thru the roof - removing the curious horizontal section - and getting the original roofer back to flash it, if only to maintain the warranty.
 
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