How to resolve wet vent back flow?

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  #1  
Old 10-13-18, 06:29 AM
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How to resolve wet vent back flow?

My kitchen sink has a garbage disposal and often times when we used them, it back flows out through the wet vents and stinks up the whole kitchen. What's the best way to resolve? I saw this video from This Old House. It seems they use a mechanical vent. However, will this work in my situation where not only air is coming back up but water and solids?
 
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Old 10-13-18, 02:40 PM
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it back flows out through the wet vents
What is a wet vent ? Do you have a Studor valve like shown in that video ?

Where is it...... under the sink ?
That type of valve is supposed to seal off the flow of anything coming out. I'd imagine if you had a drain line issue and that valve kept getting wet with greasy water..... it would become gummed up and no longer seal properly. As far as I know.... the water should not be coming up that high and if it does it's because it's not draining properly.
 
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Old 10-14-18, 10:16 AM
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This is what I have. I took two images, left and right side . How do I know if the pipe that is used for the drain hose from the dishwasher is a vent pipe or not? This pipe is where all the back flow comes out of and stinks the whole place. Can I redirect this dishwasher drain hose to the food disposable unit with that little thing on the side? Is that thing meant for the dishwasher drain hose? If so, any idea why the previous owner chose to NOT use it and instead drop the drain hose into the vertical pipe? The ultimate goal is to cap or remove that vertical pipe so there is no chance any fumes, liquids, or solids can come back up. What are my options? Any suggestion is much appreciated.

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Last edited by PJmax; 10-14-18 at 11:30 AM. Reason: added red lines
  #4  
Old 10-14-18, 10:45 AM
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Well, it looks like that vertical pipe could be a air gap pipe but, why is there is no cap on it? The dishwasher discharge hose just go right into it.
 
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Old 10-14-18, 11:00 AM
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it back flows out through the wet vents and stinks up the whole kitchen. What's the best way to resolve

I don't see a vent anywhere under the sink. What you are labeling as a vent is just the dishwasher drain although not a correct one. Notice also that what you label as a vent has a trap. You could not even install a studor AAV vent without first removing the trap that blocks the flow of air. I believe your problem is twofold; a partially clogged drain and an improperly installed dishwasher drain which should connect to the disposer. You point out in the picture right where the dishwasher drain should connect. InSinkErator makes them that way for a reason.
 
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Old 10-14-18, 11:10 AM
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I'm not the plumbing pro here.... just going by past experiences.

You have three trapped connections going to the wall. Left sink/disposer, right sink and dishwasher. There shouldn't be a Studor vent on a trapped line. That type of vent goes between the trapped device(s) and the main drain.

The puzzling part is that if there is a vent valve on the right line..... how is the dishwasher connected ?
That just looks like a trapped line and the dishwasher is just dumping into it. No vent necessary with an open trapped pipe. Maybe you're smelling the dishwasher water laying in that trapped line.

You should have a vent line going up inside the wall where your three drain lines connect.
 
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Old 10-14-18, 11:13 AM
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Yes, from a couple of youtube videos I've watched, that pipe seems to be the dishwasher air gap pipe. And you are right, it appears to be that it was not installed correctly. If in fact it's a air gap pipe, it should go all the way to the counter top with a cap and pointed down to the sink for any spillage. Second, the dishwasher discharge hose should be connected to the garbage disposal. So, the way that my plumbing is setup/connected, do I extend the air gap pipe up to the counter top? Or, can I just totally remove the air gap pipe and connect the dishwasher drain pipe to my garbage disposal? The way it is with my garbage disposal, can I just simply remove the dishwasher drain hose and connect it to the garbage disposal on that smaller opening side? Do I need to do anything else as far as the dishwasher drain hose connecting to the garbage disposal unit?
 
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Old 10-14-18, 11:18 AM
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By the way, I should mention that the only time when I have back flow issue is when my kids/wife have a sink full of water (because there are already a lot of stuff in the food disposal unit so water drain very slowly) and then they flip on the switch to run the food disposal. My house was build in 1995.
 
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Old 10-14-18, 11:31 AM
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My point is that the right line is NOT an air gap or vent line. Nor can it be. It's just a standing trapped line.

A Studor vent gets installed between a trapped line and the wall.
I drew red lines on your original picture. That would be where a vent would have to go.

You should connect the dishwasher to the disposer and cap that line completely.
I'm still fairly certain you have a drain line issue in or at the wall.
 
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Old 10-14-18, 11:54 AM
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Thanks, PJmax! Would it be more efficient (or does it matte), if I replace the three trapped connections to just two? As for the food disposal unit, the dishwasher drain inlet has no capped currently, how is it that liquid or air not coming out of that inlet?
 
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Old 10-14-18, 01:17 PM
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The disposal has a plastic knockout inside the connection fitting that needs to be removed before hose connection.
 
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Old 10-14-18, 03:38 PM
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This is how a double sink and disposal are usually plumbed. The AAV (Studor vent) should be as high as it can be. The goal is to have one trap, so when draining another sink doesn't pull the water out of the trap. The dishwasher should go right into the disposal.

I'm not sure if the triple-trap is code-compliant anyway... I've always learned that it's not the desired setup.
 
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Old 10-14-18, 06:23 PM
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I should mention that the only time when I have back flow issue is when my kids/wife have a sink full of water (because there are already a lot of stuff in the food disposal unit so water drain very slowly) and then they flip on the switch to run the food disposal. My house was build in 1995.

The house was built in 1995 so I have no reason to think you do not have a proper vent already in place up through the wall and out the roof. If it was plumbed correctly, which may be in doubt considering what it looks like under the sink, you do not need nor should you install an AAV (Studor vent).

I would never run my disposal while draining a full sink of water from the other side. Yes, it should work, but would be very slow and an improper dishwasher drain, like you have, would probably get a back flow of the whole mess. It sounds as if you are filling the disposer with waste before running it which is also wrong. The disposer should be running with the cold water running as you place food scraps and such in it.

You should remove the existing trapped dishwasher drain and cap it off solidly. Then, remove the plug from the disposer's dishwasher inlet and connect the dishwasher drain to it.
 
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Old 10-14-18, 09:00 PM
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Thank you so much, guys! Learning so many things from this single thread.
 
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Old 11-15-18, 07:01 AM
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Okay, after some thoughts. I've decided to remove the triple traps and reroute the dishwasher discharge line to the disposal.

So, to knock out the inlet in the disposal, I have to take the disposal completely out to remove the inlet plug, correct? Second, does the dishwasher discharge line have a one way flow? Another word, is there a chance water will flow back into the dishwasher? What other considerations/cautions should I take when performing these changes? And just curiosity, is there any logical reason why the previous owner set it up this way with triple traps?

Thank you for all the help.
 
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Old 11-16-18, 12:41 PM
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is there any logical reason why the previous owner set it up this way with triple traps?
Not that I can think of. Maybe a theory if one gets blocked, the others will drain, but it's not code compliant, and I think your updated plan is better anyway.

You may or may not need to remove the disposal to knock out the plastic plug. A screwdriver and hammer should do it pretty easily - but please unplug it before reaching into it to pull out the plug.

The dishwasher drain should loop up to as high as possible before going into the disposal. This will prevent any backflow.
 
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Old 11-16-18, 02:09 PM
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Thanks for the help again. So, I was thinking that perhaps I don't need to remove the whole three holes to one hole female PVC that goes to the wall. I could just remove the section that I don't need and plug the third hole However, it does not look like it's threaded. So, in this case, what's the best way to remove it?
 
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Old 11-17-18, 09:45 AM
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I could just remove the section that I don't need and plug the third hole However, it does not look like it's threaded. So, in this case, what's the best way to remove it?

Cut it off and glue a cap on it.
 
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Old 11-17-18, 01:53 PM
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Cut the unneeded side off and glue on a clean out adapter with a removable screw cap. The main reason this is all happening is that your sink drain line is partially clogged. Did you snake it out? Although your setup is wacky and not code it would have likely caused you no issues if the drain was fully open, even when dumping a full sink of water.
In my side of the world, all dishwasher discharge hoses are required to go through a sink top air gap before it connects to the garbage disposal. It is designed to stop the 'ant march' of bacteria from your disposal back to your dishwasher. If you are just high looping the discharge hose be sure to get it as high as you can, kiss the bottom of the countertop with it, because water can slide back into your dishwasher otherwise.
 
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Old 11-19-18, 05:37 PM
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Paulypfunk, that sounds like a better setup with the dishwasher discharge hoses go through a airgap to the sink. Do you happened to have a picture showing this setup so I know what to purchase or install mine? Thank you so much!
 
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