Dishwasher gurgling when sink drains

[mp2]

Hi all,

I have an issue when I drain a large amount of water in the sink (emptying a large bowl of water, or filling the sink with water and pulling the stopper) I get a brief gurgle coming from the dishwasher.

• The gurgling only last for a few seconds after the draining starts, then stops while the sink continues to drain
• I don't get any gurgling when running the faucet
• The dishwasher drain is connected via the disposal and uses a high loop
• I am using a bow vent / island vent
• The disposal tailpiece is 1 1/2" and from the p-trap and beyond everything is 2"
• The sink drains at an acceptable rate, in my opinion

I have tried putting ice in the disposal and running the disposal while dumping a large amount of water in the sink, trying to flush out any debris in the p-trap, and there was no change in the dishwasher's gurgling.

I suspect the issue is a blocked or partially blocked vent.

Is it possible the disposal is designed in such a way that a large slug of water cannot drain quickly enough through the disposal, leading to a temporary, small pressure buildup in the dishwasher drain line?

I am not a plumber, and would appreciate what you all have to say before I go any further.

 

[James Henry]

Is it possible the disposal is designed in such a way that a large slug of water cannot drain quickly enough through the disposal, leading to a temporary, small pressure buildup in the dishwasher drain line?

Yes, it's never the vent.

 

[Sponsor]

 

[mp2]

Update: Thankfully I had the foresight to install cleanouts on both the drain and vent side piping in the sink cabinet.

My initial guess being a clogged vent, I removed the vent side cleanout so it was open to the air, checked for and found no obstructions at the top of the bow vent, and then dumped a slug of water down the sink drain. Result: gurgling is still present in the dishwasher, so I think vent issues could be ruled out.

Now I am at a bit of a loss as to what the issue is. I drained the p-trap and there was no debris what-so-ever. The sink drains quite quickly, it will empty several gallons is just a bit more than a few seconds. And it is definitely positive pressure causing the gurgling in the dishwasher, IE air/water is being "pushed" back into the dishwasher.

 

[WorthFlorida]

Is this something new or always had the issue? Anything changed recently? What is the brand and model of dishwasher?

I believe the problem is in the dishwasher. With it in the off mode, the valve (solenoid) to the drain hose should be closed. Each brand does it a little different so the model number is needed to look at a parts diagram.

 

[mp2]

Is this something new or always had the issue? Anything changed recently? What is the brand and model of dishwasher?

All of the plumbing is less than a year old. Nothing has changed recently. I can't say if it's always been this way, I think I noticed it only now because of the dishwasher being open while I was draining the sink, typically the dishwasher is closed.

The plumbing is exposed in the basement, and the entirety of the bow vent is is still pitched correctly.

The disposal is an InSinkerator 1/2 HP Badger 5. The dishwasher is a GE Adora DDT595SSJ0SS

 

[Reach4]

Gurgling is a sound. If that is your only symptom, I would ignore it, or close the dishwasher door.

 

[J F]

...Is it possible the disposal is designed in such a way that a large slug of water cannot drain quickly enough through the disposal, leading to a temporary, small pressure buildup in the dishwasher drain line?
View attachment 74142

That's my guess. Since it looks like the dishwasher drains into the inlet of the disposal, I'm guessing the disposal unit is imposing a slight flow restriction... more than the sink's drain. No big deal. But of course when you pull the stopper out of the sink's wide-open (and relatively unrestrictive) drain opening, as soon as the sink water hits the relatively restrictive disposal, there will be some sink water rushing backwards through the dishwasher's drain hose... at most until the water level in this hose (towards your high loop) matches the water level of the sink. (In reality, it will be a little lower, because this backflow will be pressurizing the air in your dishwasher's high-loop (non-vented / non-air-gap) drain hose.)

The dishwasher probably has a small amount of residual water inside the drain pump and lower portions of its plumbing. When the sink water flows backwards into the drain hose, the pressurized air in the hose will bubble out through this residual water in the dishwasher... assuming no check-valve, or a faulty check-valve; see below. That's likely what's making the gurgling sound you hear.

Some dishwashers (maybe all?) have a one-way check-valve on the drain line. (Mine implements this with a rubber flapper.) This is supposed to stop any backflows contaminating the dishwasher sump. If this check-valve truly seals, it would also stop pressurized air flowing back and gurgling/bubbling out the sump. So if your dishwasher does indeed have such a check-valve, the gurgling may be a sign that the check-valve is faulty or jammed open with gunk.

 

[Tuttles Revenge]

Update: Thankfully I had the foresight to install cleanouts on both the drain and vent side piping in the sink cabinet.

Wait... you installed cleanouts.. did you Clean Out the Drain? After determining that the least likely problem was indeed not the problem (vents are never the problem)

 

[Jeff H Young]

We install an airgap so would never experiance this problem on an up to code install. Dont know your Mass. Code assuming your hose running high full of dirty water gets pressure causing a gurgle likely means a bit of dirty water going back in the D/W past whatever type of check is on the machine Im not an ap-lliance repairman or engineer . but everyone today belives the high loop is suffiecient. I think the reason UPC requires an airgap is to prevent this from happening but just guessing other places think its not needed