Plumbing mystery

AZjeff

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The kitchen sink drain in our 4 year old house has been slowing down recently and yesterday it stopped draining. It happened when a large bowl of water was emptied after being used to wash other pans and utensils. I had previously taken the trap and other pipes off and found no blockage, just some normal goop buildup. There's a fairly long horizontal run before it goes into the wall that had me concerned. I have a small 20' drain snake that I got all the way in and spun it and nothing felt obstructed. Brought the garden hose in and squirted full power into the pipe and it took it for 30-40 seconds no problem. Put all back together and dumped a bowl of water and it immediately plugged and had standing water in the sink bowl. Huh? Got a clean plunger we happen to have and had wife hold a stopper tight on one bowl and I plunged the other and couldn't force water down. What the...?? Took it all back apart looked all over, snaked, hosed, all good. Just about ready to decide to call a plumber today and remembered seeing something between the bottom of the sinks and the drain where it goes into the wall. It's a sewer drain vent fitting that eliminates the need for a vent pipe. It was screwed into 1&1/2 pipe but wasn't glued in so what the heck, dumped a bowl of water in the sink, unscrewed the vent thing and the water drained like a college boy chugging beer. This thing is some kind of one way valve, like a sewer PCV valve apparently and it must have a spring and plunger inside. Screwed it back in and the drain stops up. I can see why they'd use it as the sink is in a corner of the countertop on an outside corner of the house with 2 windows. Got one coming then this one will be dismembered for autopsy. Kinda reminded me of someone's problem with a disposer draining (GON?). Pretty happy I remembered seeing that thing before I called a plumber in. No idea how long these things have been around but remember it if you have sink problems sometime.

sewer vent.jpg
 

JTK

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My home has at least one of those that I know of. I've seen it suggested here and otherwise that the best you can get are by studor.
 

AZjeff

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This is a rebranded Studor, says Studor in the casting on top. Studor has a lifetime warranty unless sold under a different name. Probably $150 ahead buying a new Studor and not having to call in the plumber. And learned something new.
 
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Is that legal? Won't it dump sewer gas into the room? Don't codes require the vent go through the roof or at least to the outside?
No, it is a one way air check-valve. Air can enter the drain system, but gas cannot escape through the air admittance valve. It meets plumbing codes in most states when installed at least 4 inches higher than the horizontal drain line.

Air Admittance Valve Plumbing Code
 

JTK

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Is that legal? Won't it dump sewer gas into the room? Don't codes require the vent go through the roof or at least to the outside?
I'm sure there's municipalities that don't allow vents like these, but they're designed to only let air in and nothing out. They're a spring loaded check valve.

The problem is, a lot of them are not properly installed. They should be installed on a riser pipe, higher than the water level can get for the device the air admittance valve is installed on.

I have one that's badly mounted below and upstairs bathtub. I didn't know it was there until it leaked water one day. I have to re-route it at some point. Add it to the list. LOL
 
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No, it is a one way air check-valve. Air can enter the drain system, but gas cannot escape through the air admittance valve. It meets plumbing codes in most states when installed at least 4 inches higher than the horizontal drain line.

Air Admittance Valve Plumbing Code
Is this something new? Why wouldn't builders use it everywhere instead of punching holes in the roof.
 

AZjeff

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Is this something new? Why wouldn't builders use it everywhere instead of punching holes in the roof.
So hard to search..

"Developed in Sweden in the early 1970's, the air admittance valve was later introduced into the United States about 1986. Millions of these valves have been installed, which has led to significant cost savings."

They're good until they go bad. I bet millions of homeowners have no clue they have one under a sink or behind a tub or where ever. I've owned 5 houses with who knows how many vent stacks that never went bad or got plugged, I've owned one AAV for 4 years and it went bad. Not too impressed.
 
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They are a alternative in situations where a vent is not feasible but it seems some contractors use them as a easy out. I wonder how plumbing codes address these things?
 
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Get a replacement. Do not get another mainline brand unit. I have had issues with mainline products. Get an Oatey brand vent. Cost double but works great.
 
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They are a alternative in situations where a vent is not feasible but it seems some contractors use them as a easy out. I wonder how plumbing codes address these things?
They make auto vents that meet National Plumbing Code. Oatey meets the code. Some jurisdictions will not permit the use of them when a vent can be easily run during construction.
 
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So when these are installed instead of a main vent they are located at every sink and tub drain around the house?

They shouldn’t be used like that. A vent stack is the proper way to vent and all the building codes go with that.

One example where these could be used would be a island sink that is located far from the vent stack. That’s the only example I can think of right off the top of my head,
 
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Out of curiosity what brand stopper do you have and if you remove stopper and replicate your large water dump does it take it no problem?
 

AZjeff

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Out of curiosity what brand stopper do you have and if you remove stopper and replicate your large water dump does it take it no problem?
Not sure what brand or why it would matter, it's whatever brand came with the sink. The sink will plug with the AAV installed no matter whether both bowls are open or not and when water is run into either bowl. Looks like this:
.
stopper.jpg



Try a shop vac have had good luck with using one with trap pulled.
The drain isn't plugged, it's the bad AAV. Will using a shop vac fix the air admittance valve?

The plumber didn't cut corners, the AAV was used appropriately. My daughter has one under her peninsula sink as you'd expect knowing about their intended usage. This device allows architects to put sinks in places that would have been problematic or impossible before but adds a failure point to a normally failproof system.
 

JTK

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@AZjeff Just a suggestion, but if you don't need the stopper function often for your sink strainer, I'd highly recommend a Dripsie brand sink strainer. They're exceptional IMO. All my sinks have them after going through every other strainer under the sun.
 
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Similar issue with a Kohler Duo Strainer. Works fine without, but drains slow as molasses when installed and lots of water or hot water from pot of noodles for example is poured in. Maybe should of included the reason for the question. 🤷‍♂️ GL
 
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