AAV replacing vent for island

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Andrew123

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Hi All,

I’m renovating my kitchen and would like to know if I can cap off my old vent and install an Aav in its place. The picture is the back of my sink. I’ve cut off the vent that used to be routed through the roof. My plan is to cap that off and put an aav underneath the sink. Is this ok or will I have problems??

thanks

Andrew
 

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Mliu

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An AAV is never as good as a real vent. Also, some AAV's make an unpleasant sound like a whoopie cushion when the sink drains.

Is the reason for eliminating vent because you're making your sink counter into an island? Look at island venting.
 
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Andrew123

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Great thanks for the advice. I have one other question.. If I cap off the old vent line sticking up on the right side of the picture, will this cause an issue with trapped air? I plan to put the AAV (or now island venting) inside the sink cabinet. Thanks!
 

Mliu

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If I cap off the old vent line sticking up on the right side of the picture, will this cause an issue with trapped air?
No problem capping that off. Make sure you use purple primer on all solvent welded PVC joints. I don't see any on the existing piping.
 

Andrew123

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Awesome, thanks mliu. Yeah, I'm guessing the existing plumbing was installed almost 30 years ago when the house was built.
 

Reach4

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Andrew, what is going to be on either side of that cut-off vent? You could put a removable grill next to an AAV, and that would both vent the AAV and leave it accessible for replacement.

Your under-sink AAV with the proper connection there works with your proposed capping just fine too. In that case, I suggest you post a sketch of your proposed AAV and trap arrangement.
 

Mliu

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I'd go with island venting. AAV should be a last resort only when a real vent is impossible or impractical. Considering the amount of remodeling being done here, and assuming you have access under the floor, an island vent should be both possible and practical.
 

Andrew123

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Good idea Reach4. I was trying to think of way to do that. I like the idea of a removable grill.

mliu, At this point running a vent under the floor is highly impractical since I'm on a concrete slab. Can I ask why the AAV is not recommended? I've actually been using my sink without the AAV, just like the picture and the only sounds I hear are when I dumped a big pot of water there was a little gurgling. I haven't had any strange smells.
 

Mliu

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At this point running a vent under the floor is highly impractical since I'm on a concrete slab.
You didn't mention the concrete slab floor in your original post. In this case, an AAV is probably your best solution.

Can I ask why the AAV is not recommended? I've actually been using my sink without the AAV, just like the picture and the only sounds I hear are when I dumped a big pot of water there was a little gurgling. I haven't had any strange smells.
1. An AAV is a mechanical device. Mechanical devices require maintenance and are subject to failure. A true vent is simply a pipe open to the atmosphere and is essentially maintenance-free.

2. If an AAV fails, it can allow the release of unpleasant and flammable/toxic gases (e.g., methane, hydrogen sulfide) into your living space. A true vent releases these gases outside the building envelope.

3. An AAV typically has a poppet valve or a rubber diaphragm to allow the one-way admittance of air into the drain pipe. As the water travels down the pipes, it creates a suction in the piping above the draining water. This suction causes the AAV valve to open to allow air into the pipe so the P-trap is not sucked dry. As the poppet or diaphragm opens, it quickly relieves the suction and the valve may close again. Then the suction builds and the valve opens and closes again. This can happen very rapidly and may create a sucking/vibrating sound like cow flatulence. Not exactly something you want guests to hear in the middle of your dinner party.

Regarding point #3, there are a lot of AAVs on the market and designs change. Hopefully, they have improved to the point where this sound is uncommon. But I have heard AAVs make this sound before.

As for leaving that vent pipe open, I would strongly recommend against doing that, even temporarily, if you are living in the house.
 
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