New bosch dishwasher squeal after draining

[stylgc]

Hi-
Hope someone can help. This is the 2nd bosch dishwasher I have owned that is making a squeel "erp" sound almost like a "seal barking" noise after the drain motor stops. Noise is coming from the diswaher.
The dishwasher is connected to its own drain on a stand pipe. The noise only happens after the drain pump stops. This 2nd bosch is brand new and it makes the noise, so I figure there is something in our plumbing set-up causing this. I have used another brand of DW for a while and it did not make this noise-only the bosch does this. Also, I can reproduce this sound if I move the drain hose up high then move it lower.
Please see the attached .jpg for our set-up.
You will see in the photo that there is a vent cap on top of the stand-pipe-I have also tried to remove this so there is more air flow behind the water>still makes the squeel.
Can someone please verify that this is a correct plumbing setup for a dishwasher.
thanks.

 

[Seaofnames]

Could be the sound of your AAV opening up and letting in air. I'd also move that as high up as you can get, or attempt to put in a real vent.

Have an appliance tech come out and check it out...warranty?

 

[Sponsor]

 

[Terry]

The AAV should have been before the p-trap.
Where the 90 is, there should have been a tee, and then the AAV would have been above that.
The AAV also needs air. If the seal is tight to the cabinet, it won't be able to draw air.

 

[Geniescience]

A standpipe / indirect drain is what you need -- because the DW drain isn't combined with a sink drain tailpiece in this image.

Only an open pipe can do this. Go look at how your washing machine drain is connected.

Or an air gap (AAV's cannot be used for an air gap, as they don't let air flow both ways.)
Or a Johnson Tee if you want to put the draining-sucking-gurgling noise outdoors. (Or some other long-piped opening to put the noise somewhere else).

The AAV has to be on the other side of the P trap, as Terry said.
The AAV being on the other side of the P trap is unrelated to this first point I made here.

Hope this helps.
.

3rd point: could be serious. You didn't draw any venting in the red part where (I guess) you simulated the pipe configuration you have. Please say you have a lot of venting.

 

[stylgc]

dw noise

Hello-
Thanks for the replies-
I am a newb so bear with me.

1. when you mentioned the aav before the P-trap, because this plumbing is in the floor and there is no basement access am I SOL?
2. should I take off the AAV and leave the pipe open or should this be capped? or should I install an air gap-
3.If I install an air gap-should the pipe in the photo(where the aav is now) be capped and only a drain hose is attached to the abs down pipe?

I thought there needs to be air on a drain pipe(like a dishwasher set up when connected to a sink) for water to be pushed down.

-I thought this set up was modeled after the stand pipe method-like my washing machine. drain hose in abs pipe.
-there is a abs venting pipe connected to this pipe 12 feet across and 9 feet down. It shares a vent with my basement bath.
-yes, it does sound like air is being pushed back into my Dishwasher(sound is coming from my DW)-will the air gap installed as high as possible under the counter solve this?
-How is this set up different from a Dishwasher that is connected to a sink? my sink does not have an AAV-the vent to the outside is very far from the sink.

Thanks again.

 

[Jadnashua]

An AAV only lets air in, not out. If there is any obstruction, pumping high volume of water out of the DW, it could pressurize the pipe...the AAV can't let the air out, where a normal vent can let air both in and out. When the pump stops, things try to go back to equilibrium.

The vent is designed to prevent suction in the p-trap. As noted, where yours is won't do that at all. The objective is to prevent it being sucked dry and letting sewer gasses past the trap. that's another reason why the AAV only lets air in. If it could also let air out, it would be an open air vent into the sewer.

 

[Geniescience]

go look at the OPENING allowing air to move in or out, at your clothes washer.

then you may agree that you did the wrong thing by closing off your standpipe.


2.
All discussion of AAV has to do with the sewer gas side of the P trap, not the room air side of the P trap. That will be the "other side" of the P trap.

One side is room air, OK to breathe.
One side is sewer gases, not OK to breathe and potentially lethal / harmful to health / disease / etc.


don't have time to answer each indiv. question.

 

[stylgc]

all good

I removed the drain hose from the side fixture and put the drain hose directly in the top of the stand pipe(like my washer) and all is good-No more noise is coming from my DW.
Many thanks

 

[Geniescience]

The squeal noise was caused by air coming out. The AAV prevented air from exiting.

You still need to rework your drain line. AAV, venting.

The numbers in your diagram don't add up.
12', 15', 9' etc.
Other things don't make sense too.

 

[stylgc]

hmmmmm...............

The plumber has the kitchen sink and the DW draining on separate abs pipes that runs across my kitchen(approx 12'-15' for both) to the other side of my house>then the Dishwasher abs drain pipe goes down 9' to the floor- down to the basement>it is then connected by a 45 degree elbow to a larger diameter ABS drain pipe. The drain pipe goes all the way through to my roof which I assume is the vent.
The DW gets its water from a 15' 3/8 copper tube which runs through my floor joists to the kitchen sink area. Would have been nice if they designed the kitchen with the DW beside the sink instead of the other side of the kitchen.
Does this sound right?
Thanks

 

[Jastori]

The main problem (based on the info you gave so far) is that the DW drain does not have a vent to protect the trap from siphoning dry. The vent needs to be on the downstream side of the trap. Your drain should work fine, but there is a chance that the trap could be siphoned dry - if this happened, you would likely be able to smell it. If it doesn't happen, then there is no urgent need to change what you have now, although it is not to code. Depending on your local codes, you may or may not be able to use an AAV in place of a true vent.

 

[stylgc]

Thanks, Just one more question> when I stuck the DW drain hose in the top of the stand pipe, isn't this the exact set-up as my washing machine? what would be the difference with this set-up
Thanks again

 

[FloridaOrange]

Thanks, Just one more question> when I stuck the DW drain hose in the top of the stand pipe, isn't this the exact set-up as my washing machine? what would be the difference with this set-up
Thanks again

Your washing machine box drops 20" or so down to a trap. At the vertical where the trap is teed off from there is a vent on that line.


Or at least there should be.

 

[stylgc]

I see-my washing machine is vented 2 feet after the P-trap.
My dishwasher is vented waaaaay down the line. Vent line is attached to the DW drain line 12 feet across and 9feet down. So, I am guessing this is too long of a distance for a vent to be connected after the p trap. The squeel has returned. If this line needs to be further vented, Is there another solution to this-or am I going to have to rip up the floor under my cabinets and add a vent line closer to the p trap?
Thanks

 

[FloridaOrange]

To do it right you should have an island vent loop. On a 2" line the trap can be a max 6-8 feet in most codes.
Search this site for island vent.