Plumbing vent terminates in side attic

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Old 04-07-15, 11:12 PM
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Plumbing vent terminates in side attic

Hello,

I have a 1 and 1/2 story house with two side attics that run along the length of the house. The side attics have spray foam insulation on the underside of the roof, and are enclosed; this is not an attic vented to the outside.

In one side attic, the bathroom plumbing is all properly vented through to the roof. In the other side attic, the kitchen sink vent terminates within the attic. To be clear, I have not had any problems with the current venting set-up - I'd just like to tidy up any code infractions that I am aware of.

I am attaching a picture that shows the kitchen vent terminating in the side attic. I didn't bring a tape measure, but it looks like a 2" diameter pipe.

Possible solutions:

1. Do nothing - if it ain't broke, don't fix it.

2. Run the vent horizontal in the joist space to the other side attic to connect with main vent (about 15 feet) - would look tidy, but is a horizontal run code compliant?

3. Add a one-way vent (suggested by home inspector) - is this called a studor vent?

4. Cut a new vent hole to exit the roof (would prefer to avoid this option, if possible).

What is the right course of action? Thank-you for your time.
 
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Old 04-07-15, 11:26 PM
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Running the horizontal to the existing through-roof vent is the preferred method. Make sure that you have a slight slope on the pipe, about 1/8 to 1/4 inch downward towards the pipe going down in the house.

Or you could use a Studor (name of company that makes them) or other brand of Air Admittance Valve. The latter is not the preferred method because it is a mechanical device and can fail. As such it must always be accessible.
 
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Old 04-08-15, 05:12 AM
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I agree with Furd. I would not cut a new hole in an otherwise non leaking roof. If it is feasible to tie it in to an existing vent with proper slope, that would be plan A. If not, then a Studor vent would be a close second. Should you ever encounter drainage slow down, keep in mind the AAV may have failed and will need replacing. They screw off, so no problem there.
 
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Old 04-17-15, 05:02 AM
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Should you ever encounter drainage slow down, keep in mind the AAV may have failed and will need replacing. They screw off, so no problem there.
I have only one Studor in my current house, and in all the houses I've owned I've never had one fail. What is the typical failure mode?? Considering how they work, I'd expect them to fail open, in which case you'd never know unless you periodically inspect them.
 
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Old 04-17-15, 10:27 AM
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Air admittance valves are a fairly new addition to the plumbing codes and some jurisdictions still do not allow their use. Because they ARE a mechanical device there is always the possibility of failure, albeit slight. I am unaware of any long-term testing that would place any kind of expected lifetime on AAVs. They might last for fifty years or more but I don't think anyone could predict with any degree of certainty any kind of expected lifetime.
 
 

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