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Dishwasher Drain


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IPC 802.1.6 Domestic dishwashing machines: "...or discharge into a wye branch fitting on the tailpiece of the kitchen sink or the dishwasher connection of a food waste grinder." Which means the connection must be made before the p-trap to prevent sewer gas from coming in this way.

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Any reason why the dishwasher couldn't be hooked up this way?

Download Attachment: icon_photo.gif PlumbDWDrain (Medium).jpg

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I believe that configuration would be acceptable matching the intent of the code. It would be a smoother connection and would reduce the potential of stop-ups in my opinion because you would not have to deal with the pipe size reduction caused by the baffle in a wye branch tailpiece.

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Isn't the drain line for a dish washer supposed to attach to drain line before the trap and not in a basement drain line.

Not just the dishwasher. Every plumbing fixture has to drain via a trap per IRC P3201.6

- Jim Katen, Oregon

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I believe that configuration would be acceptable matching the intent of the code. It would be a smoother connection and would reduce the potential of stop-ups in my opinion because you would not have to deal with the pipe size reduction caused by the baffle in a wye branch tailpiece.

I agree that it's an ok installation, but it's not superior to a wye at the tailpiece. I've never seen a wye with a baffle. Are you sure that you aren't thinking of a Tee with a baffle?

- Jim Katen, Oregon

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A tailpiece with a dishwasher wye fitting has a baffle to divert the pressurized discharge from the dishwasher toward the trap and prevent it from spraying up through the strainer basket. If the tailpiece is pvc you should be able to see it looking down through the sink.

Rob that drain set up, although beautifully executed, is a pretty expensive way to run a drain. I count 11 fittings and lengths of pipe before the trap. As a nice bonus the only way to open the trap is to drop the entire assembly.

Tom

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Isn't the drain line for a dish washer supposed to attach to drain line before the trap and not in a basement drain line.

The dishwasher drain line is covered under Section 807.4 in the UPC.

No domestic dishwashing machine shall be directly connected to a drainage system or food waste disposer without the use of an approved dishwasher air gap fitting on the discharge side of the dishwashing machine. Listed air gaps shall be installed with the flood-level (FL) marking at or above the flood level of the sink or drain board, whichever is higher.

In Oregon it was covered under Section P3029.3

A domestic-type dishwasher having a pump for the removing of waste water may discharge over the sink or, if the discharge pipe from the pump is extended to the underside of the cabinet top and securely anchored to preclude the danger of sink waste water from flowing back into the dishwasher, it may be connected to a fitting or other inlet between the sink and sink trap. The discharge pipe extending from the inlet side of the sink trap shall be copper tube or other material approved for such purposes.

I thought there was another code ref requiring connection to the disposer if present, but now I can't find it.

Chris, Oregon

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Have not seen an air-gap in Mid-Michigan for 10yrs. No code reference, but in fact most jurisdictions don't allow connection to a food waste disposer. Nearly every dishwasher simply has the discharge line higher than floor of kitchen sink.

I would write the original photo as defective - just my opinion.

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A tailpiece with a dishwasher wye fitting has a baffle to divert the pressurized discharge from the dishwasher toward the trap and prevent it from spraying up through the strainer basket. If the tailpiece is pvc you should be able to see it looking down through the sink.

Whenever I've seen one of those, it's been a tee, not a wye. They need the baffle because the dishwasher connection approaches the tailpiece from a near 90-degree angle. If it were a wye, it wouldn't need the baffle because the connection would be approaching from 45 degrees.

- Jim Katen, Oregon

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A tailpiece with a dishwasher wye fitting has a baffle to divert the pressurized discharge from the dishwasher toward the trap and prevent it from spraying up through the strainer basket. If the tailpiece is pvc you should be able to see it looking down through the sink.

Rob that drain set up, although beautifully executed, is a pretty expensive way to run a drain. I count 11 fittings and lengths of pipe before the trap. As a nice bonus the only way to open the trap is to drop the entire assembly.

Tom

Does anybody have a photo of a baffled dishwasher fitting?

Tom, that's our standard installation.

How do you hook up your dishwashers where you are?

Of course, if you want to save money you could always do it this way.

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In higher end homes when they spend the value of a new 1970 Volkswagen beetle then I suggest to install a dishwasher 'muffler' to eliminate drain noise.

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This is the norm around here

http://images.lowes.com/product/046224/046224005261.jpg

There is a baffle just above the dishwasher attachment that angles downward and covers just shy of half the drain diameter and directs the discharge away from the basin and towards the trap.

The DWV typically ends at the wall and the trap and drain are this smaller lighter material connected with slip joints.

Tom

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