Can you identify Loud Dishwasher drain noise from airgap?

[Modernwood]

When my dishwasher drains, there is a loud dishwasher drain noise. It's a gurgling sound emanating mostly from the airgap. The dishwasher drains to the airgap, which drains to a junction at the top of the disposal.

Here's a YouTube link to the offending sound. At the end, I cover it to show noise dampening.

I get that there's gonna be "a" noise, but this is so noisy that we have to pause the TV and wait twenty seconds. I've been trying to diagnose it and fix it myself for two days with no real luck. I'm willing to call a plumber but the ones I've spoken to suggest all the things I've tried and I'm hesitant to pay someone hundreds to go fishing for a few hours trying to solve it themselves.

Here's what I know:
1 year old Bosch 800 series ultra quiet Dishwasher rated for 40db. (I'm aware that's not rated to the drain noise, but if someone spends money to have a quiet dishwasher they don't expect it to be loud during some parts and for sure my rich friend's dishwashers aren't this noisy). Meanwhile, in so many posts about noisy draining, there's always one a-hole who says, "It's water, it's supposed to be noisy, stop complaining," or something to that effect. That's not helpful. Don't be that person, please. For sure people buying this expensive of a dishwasher are not living with this noise. I shouldn't have to either. And I cannot imagine everyone with an airgap is living with this either. Correct me if I'm wrong, but don't just tell me to live with it either.

One plumber suggested a clog in the drain under the kitchen. It's not that. Water drains fine with no gurgles. I snaked the drain under the sink to 25 feet. Nothing. Still drains fine.

Few notes:
-I think it's been doing this since it was all installed a year ago.
-Big stainless sink, restaurant style, certainly isn't helping the acoustics but it can't just be that, can it?
-There's no water emanating from the airgap. It's clean, not clogged and also a year old.
-The garbage disposal (insinkerator) is also only a year old. No apparent issues.
-The DW drain does have to travel like 4 feet (it's full length) to get to the airgap and then goes straight up, so I've considered maybe some backflow issue there? But all the installation stuff iv'e seen suggests this is fine.
-I've also plugged the drain itself and it reduces the sound like 10% at best.

If I cover the airgap with my hand the sound is 80% muffled so I know this is the source of the sound and it's to do with the way the water is pouring through the system but I both cannot find a fault in the setup nor does it seem that everyone else in the world is living with this noise.

Please help.

 

[WorthFlorida]

I had to remove the "feature=share" part of the URL to see the video. It seems to me just an air gap function. Air-gap's are driven by local codes. I would just connect the drain hose directly to the disposal and give it a try. I have a dead silent Bosch directly tied to the disposal and you can hardly hear the machine drain. To get the machine as quiet as possible, the water is pumped at a very slow rate.

 

[Sponsor]

 

[Reach4]

Some think some air gaps are louder than others. https://terrylove.com/forums/index.php?threads/loud-dishwasher-drain-noise-from-airgap.99927/

I would think some kind of cover could muffle some sound. An inverted lead cup would probably do it, but I don't know where to find that. How about an inverted mug or drinking glass.

 

[Modernwood]

I had to remove the "feature=share" part of the URL to see the video. It seems to me just an air gap function. Air-gap's are driven by local codes. I would just connect the drain hose directly to the disposal and give it a try. I have a dead silent Bosch directly tied to the disposal and you can hardly hear the machine drain. To get the machine as quiet as possible, the water is pumped at a very slow rate.

Thanks for the YouTube Link tip. I changed it so it should work.

So do you think that my airgap just sounds like a normal airgap? I can't imagine everyone in CA (or however far reaching this code is) is dealing with this.

Yeah I may try to tie it directly to the disposal as a last resort.

Last note. I thought I had read that Bosch pumps were super fast, not super slow (but I'm really not sure)

 

[Modernwood]

Some think some air gaps are louder than others. https://terrylove.com/forums/index.php?threads/loud-dishwasher-drain-noise-from-airgap.99927/

I would think some kind of cover could muffle some sound. An inverted lead cup would probably do it, but I don't know where to find that. How about an inverted mug or drinking glass.

I used to be an audio mixer and know a thing or two about acoustics. I need something to dampen it. Best thing would be like a rubber stopper actually plugging it. Any sound coming out is just going to reverberate in that big sink. But that defeats the purpose of the air gap entirely. (which is maybe, ultimately, what I have to defeat)

 

[Modernwood]

Thanks for the Youtube Link tip. I changed it so it should work.

So do you think that my airgap just sounds like a normal airgap? I can't imagine everyone in CA (or however far reaching this code is) is dealing with this.

Yeah I may try to tie it directly to the disposal as a last resort.

Last note. I thought I had read that Bosch pumps were super fast, not super slow (but I'm really not sure)

CAn you please chec

Some think some air gaps are louder than others. https://terrylove.com/forums/index.php?threads/loud-dishwasher-drain-noise-from-airgap.99927/

I would think some kind of cover could muffle some sound. An inverted lead cup would probably do it, but I don't know where to find that. How about an inverted mug or drinking glass.

Reach, mind please checking that link? It's just coming straight back to this page.

 

[Reach4]

Let's go with https://terrylove.com/forums/index....air-gap-noise-new-bosch-500-dishwasher.94084/

I was not thinking of a tight-fitting mug, so air and water could come out.

For blocking bass, you want mass. Other material can do a good job on higher frequencies.

 

[Helper Dave]

Sounds pretty normal (sorry). Dunno if it's an option for you, but here in WI, where air gaps are also required, we have the option of draining a dishwasher right to a stand pipe under the sink, too. This requires the kitchen sink line to be 2" instead of 1 1/2" (1 1/2" traps for the dw, and sink going into a 2" branch). In new builds, we always put them in this way, and since houses mostly have basements, it's not crazy complicated to upsize older drains for a bit of $$$. If you're on slab, and it wasn't run as 2", you'd be out of luck outside of a complete kitchen make over.

This keeps the sound in your cabinet, and helps muffle it a lot. Doesn't disturb the kitchen sink trap either, so no echo in those big steal sinks.

 

[abelrb]

Have you checked your dishwasher's backflow preventer or check valve? We had a similar gurgling problem, although not from an air gap (our house doesn't have one). Each time we used the dishwasher we'd get loud gurgling noises when the pump drained. I finally took the dishwasher apart and found that the built-in check valve right before the pump had completely eroded. Was able to replace it with a spring check valve for a few dollars and now we have no more gurgling. This might not be what's causing your gurgling issues, but if it is, it's usually a cheap and easy fix.