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Old 07-26-2020, 11:00 AM   #1
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Air admittance valve defective?


Hey guys;
I am hearing gurgling in the kitchen sink when the washer in the basement drains, and sometimes the kitchen sink gets very sluggish.
Here are the facts:


1. The kitchen sink and laundry room tub in the basement (the washer drains into the tub, not directly into the pipe) share a secondary stack in the laundry rm.


2. There is a vent pipe to the roof which connects to the laundry tub line just before it enters the stack.


3. After the laundry stack, there is a horizontal pipe running under the basement floor to the main sewer (about 30 ft with several bends)
The first 10ft of this pipe downstream of the stack is PVC, which replaced that section of iron pipe due to corrosion and clogs.


4. The (roof) vent to the kitchen sink was blocked, so it was replaced with an air admittance valve (Redi Vent) by a plumber, who also replaced the section of pipe between the trap and the pipe down in the laundry rm.


5. All plumbing from the kitchen sink and the laundry tub, as well as the laundry stack are PVC pipe.


6. The dishwasher drains into the kitchen sink tailpiece.



Here are some photos:
1. The admittance valve under the kitchen sink



https://drive.google.com/file/d/1RaI...ew?usp=sharing




2. The laundry stack. The vertical pipe coming into the pipe from the tub near the stack is the roof vent for the laundry.

https://drive.google.com/file/d/1hD6...ew?usp=sharing


3. The kitchen sink line where it comes through the floor into the laundry rm.


https://drive.google.com/file/d/1CLK...ew?usp=sharing




This morning while the dishwasher was draining, water was coming up from the sink drain. After that, the water remained and drained very slowly.
I believe the washer (in the basement) was also draining at the same time, but not absolutely certain.


I removed the trap under the kitchen sink. It was clear.
I snaked the line from the trap to the laundry stack. I did not encounter any resistance with the snake, except for the bends where I needed to rotate the snake to get it through. It did not appear to me that there were any clogs in this line.


After snaking, the kitchen sink drain was still very sluggish.
I waited for all of the water to drain, and while the dishwasher was not draining, I ran some water in the sink. This time it went down quickly.


I have come to believe that the problem is not a clog, but a vent issue.
Perhaps the air admittance valve is defective? It should not be, as it is not even 2 years old.
Could the problem be the laundry (roof) vent?
If that pipe is partially blocked, perhaps there isn't enough air getting in when the washer is draining, which causes a problem for the kitchen sink.


I have an inexpensive 'endoscope' I can insert into the kitchen sink line after removing the trap, if that could reveal anything, but so far I have not tried it.


Any ideas?
Thanks
Ultrarunner







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Old 07-26-2020, 06:28 PM   #2
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Re: Air admittance valve defective?


The purpose of an open vent is to bring equilibrium to the drain its sometimes positive sometime negative, AAV are negative only, and can not be used is some applications, its all in the way its piped in. different sizes depending on loads.. if in the beginning it wall worked you may be looking at just a simple developing obstruction. and yes AAV do go bad..
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Old 07-27-2020, 09:41 AM   #3
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Re: Air admittance valve defective?


I guess I should check out the laundry vent pipe. I may be able to get my endoscope probe into it by removing the rubber coupling at the point where it joins the pvc pipe, but the cable is only 16ft, which will not be enough to get all the way to the top. Still, if I can just get it around the bends to the straight pipe, I should be able to see daylight coming in.
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Old 07-27-2020, 10:19 AM   #4
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Re: Air admittance valve defective?


Get your drain cleaned it is partially blocked it is summer vents do not freeze during this time.
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Old 07-27-2020, 12:59 PM   #5
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Re: Air admittance valve defective?


Sounds like a partial clog in the drain. Does the kitchen drain good with the AAV removed? If not, then it's definitely a partial clog. If it drains with the AAV removed, it's a bad AAV.
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Old 07-28-2020, 12:36 PM   #6
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Re: Air admittance valve defective?


Just a while ago, I found the kitchen drain backed up. I went down to the laundry rm and found that the tub was about 1/2 full with water from the washer (which drains into the tub).
The water in the laundry tub was draining, albeit a bit slowly. But when the water in the tub was low enough that air started getting into the drain, it made s sucking sound and the water went down much faster. This has been the case for quite some time.


So, I guess it's time to call the drain guy, as I don't have the right equipment to properly open the line from the laundry to the sewer.
I will inform the guy about what has been happening, and let him figure out whether the vent is clogged or not.
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Old 07-28-2020, 02:18 PM   #7
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Re: Air admittance valve defective?


Quote:
Originally Posted by Ultrarunner2017 View Post
Just a while ago, I found the kitchen drain backed up. I went down to the laundry rm and found that the tub was about 1/2 full with water from the washer (which drains into the tub).
The water in the laundry tub was draining, albeit a bit slowly. But when the water in the tub was low enough that air started getting into the drain, it made s sucking sound and the water went down much faster. This has been the case for quite some time.


So, I guess it's time to call the drain guy, as I don't have the right equipment to properly open the line from the laundry to the sewer.
I will inform the guy about what has been happening, and let him figure out whether the vent is clogged or not.

Easy enough to find out if it's the AAV. do what bruce said in post 5. Remove the AAV and see if it drains better. If it does replace the AAV, and you're done. It looks like it just unscrews. If it doesn't drain better you have a partial clog further down stream that needs snaking.
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Old 07-29-2020, 11:50 AM   #8
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Re: Air admittance valve defective?


It's only when the laundry tub is also draining that the kitchen sink drain gets sluggish.
That said, next time I find the kitchen sink slow, I'll try to unscrew the AAV.
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Old 07-31-2020, 07:17 PM   #9
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Re: Air admittance valve defective?


Today, I found the sink draining slowly (the laundry tub was also draining), so I unscrewed the AAV, and sure enough; the sink drained immediately. So I've got a (<2yr old) AAV that is defective.
Now, all I've got to do is determine the size. I didn't see the pipe size on the AAV, but I need to look more closely. Otherwise, I'll just measure and look up the chart for the pipe size.
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Old 07-31-2020, 08:59 PM   #10
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Re: Air admittance valve defective?


Quote:
Originally Posted by Ultrarunner2017 View Post
Today, I found the sink draining slowly (the laundry tub was also draining), so I unscrewed the AAV, and sure enough; the sink drained immediately. So I've got a (<2yr old) AAV that is defective.
Now, all I've got to do is determine the size. I didn't see the pipe size on the AAV, but I need to look more closely. Otherwise, I'll just measure and look up the chart for the pipe size.

Or plug the vent with a rag and take it with you to the store and match it up. Looks like 1.5 or 2.0. Size should be right on the vent. I see writing on it when I zoomed in. Look closely as writing is small.
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Old 08-01-2020, 11:30 AM   #11
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Re: Air admittance valve defective?


The Redi-Vent is a standard 1-1/2in NPT (according to their data sheet).
The top of the vent has "Max 20 DFU" stamped on top.
Perhaps I should buy the Oatley instead. It's about $2.50 cheaper on Amazon, and has the same specs.
But I think before I buy either, I will try to contact Studor to see if they might be able to replace it under warranty.
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Old 08-01-2020, 01:30 PM   #12
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Re: Air admittance valve defective?


I had another thought:
Wouldn't the fact that I hear water bubbling/gurgling in the kitchen sink while the laundry tub (in the basement under the kitchen) is draining be an indication that the vent (to the roof) for the laundry tub is blocked - in addition to the AAV under the sink being defective?
If the laundry vent is not blocked, then why would air be pulled through the upper part of the laundry stack in the first place? Shouldn't the laundry vent provide enough air for that tub to drain properly?
That said, if the AAV under the kitchen sink wasn't also defective, then the sink drain would not be bubbling, as air would be pulled in through the AAV and not the drain.


There is also something else I want to mention about the laundry tub:
Often, when I dump some water into the tub - which isn't nearly enough to fill the tub, but enough to completely cover the drain - the water appears to drain slowly at first, but after some has gone into the stack, the tub drains much more quickly, and then there is a sucking sound at the laundry tub drain.
Should there ever be a sucking sound at a drain? If there were enough air getting into the system while draining, there shouldn't be so much air coming in through the drain to cause the sucking.


Since I'm not a pro, and even some pro's probably couldn't diagnose this problem properly, I expect it would take a plumbing engineer - someone who actually designs plumbing systems, not just fixes them - to solve the problem.


Edit: Maybe a vacuum gauge, placed at various points on the system could tell me something?
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Old 08-01-2020, 02:09 PM   #13
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Re: Air admittance valve defective?


My bet is you have a packed drain full of grease under the slab. I would suggest you open that stack clean out and take a look with your endoscope. Also, how long is your drain snake and what size?


AAV valves are designed to only let air into the pipe. If your drain is not draining as it should it will build positive pressure and the AAV as designed will shut down the vent. They are not designed to let sewer gas into your living space.


I also noticed your utility sink vent was not done to a code legal way. It goes horizontal before it is 6 inches above the utility sinks flood level rim. This is not code legal because vents are not easy to clean and if the drain becomes slow it may fill up with derbies in that horizontal portion of the vent.


Would you please take a pic of the upper portion of that utility sink vent? Does it go out the roof or does it tie back into the kitchen stack?





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Last edited by Ghostmaker; 08-01-2020 at 02:20 PM.
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Old 08-01-2020, 05:49 PM   #14
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Re: Air admittance valve defective?


Ghostmaker;
I'm not sure what you mean by "I also noticed your utility sink vent was not done to a code legal way. It goes horizontal before it is 6 inches above the utility sinks flood level rim."
If you're talking about the pipe pictured in this shot:
https://drive.google.com/file/d/1hD6...ew?usp=sharing
That pipe connecting to the horizontal pipe near the stack is the laundry tub vent.
The horizontal pipe running from the tub to the stack is about 6ft long.
Should the laundry vent go vertical closer to the tub?


I will take some more photos to help clear up what my configuration is.


As for the pipe under the floor; it is PVC for the first 10ft after the stack, then old iron pipe the rest of the way to the sewer.


My snake is 1/2in dia and is 50ft long, but is just a snake; no motor or even a crank, so no way of rotating it.


I believe I am now understanding how this problem could be a clogged pipe downstream of the laundry/kitchen stack.
If the pipe is partially clogged, a positive pressure would be produced when water runs down from the laundry tub and begins to back up.
The AAV under the kitchen sink would not allow this pressure to escape, so it would try to escape through the trap under the sink, thus the bubbling/gurgling noise when the laundry tub drains.
But wouldn't the laundry vent prevent the pressure inside the pipe from going positive? So, perhaps that vent line is partially clogged as well?


Until now, I have been assuming that the gurgling in the kitchen sink drain was caused by negative pressure due to the failure of the AAV. I had not considered positive pressure.


So I suppose the first thing to do is call the drain guy and have the line from the laundry to the sewer roto-rootered. Then, if the problem persists, we need to consider venting issues.
As far as my 'endoscope' is concerned, I doubt it would provide me with any useful info:
First, it is only 16ft long, and second, the cable is far too flexible to push through the pipe. Thirdly, the lens will get gunked up very quickly and I will not be able to see anything. It is not what one could call a 'sewer camera'. I purchased it for other uses, such as looking into walls for pulling electrical cables, or searching under furniture for lost items.


Edit: Would this gauge work to measure pressure (pos or neg) in the drain line, assuming the proper fittings?
https://smile.amazon.com/Filled-Vacu...s%2C138&sr=8-4
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Last edited by Ultrarunner2017; 08-01-2020 at 06:01 PM.
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Old 08-01-2020, 06:22 PM   #15
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Re: Air admittance valve defective?


This is the laundry tub drain line between the tub and the (laundry rm) stack.
The pipe leaving the horizontal and going vertical near the stack is the laundry vent to the roof.
The stack drains into the pipe running under the basement floor about 30ft to the sewer. The first 10ft of this line is new PVC. The rest is old iron pipe.


https://drive.google.com/file/d/1wNq...ew?usp=sharing
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