Better Undersink Plumbing Plan & Drain Height

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Dallas, TX
I am a newbie DIY Guy working with existing cast iron drain inlet in a 1930's era kitchen. I saw an article from a veteran plumber in Fine Homebuilding. It puts the drain plumbing on the sink base rear wall, allowing for more storage. The layout looks clean. I have two questions:

1. I prefer to have a P-trap with a traditional cleanout at the bottom of the trap. Can I eliminate the cleanout that is the last connection on the downstream side?

2. When I look at the DW line connection, it makes the high loop and then goes directly into the waste drain. Where is the "air gap"? Is it because the connection is above the P trap with an air gap to either drain at the double Y? At least two posts emphasize the code does not support connecting the DW directly to a drain line. See the image below. The posts say the DW has to be connected to an air gap mounted on the sink deck or connected via a high loop to the disposal DW connection. There are prior post that emphasize, use a high loop, an air gap on the sink deck, or a Johnson T.

3. I have an issue with the existing drain height due to a deep sink and the disposal drain height similar to this post. I want to keep the sink and the disposal that I bought but I do not have a additional cleanout like the post.

The center of the 1-1/2 inlet on the cast iron pipe is at 19 inches above the kitchen floor. The center of the drain on the disposal is at 18-13/16 inches above the kitchen floor. The disposal drain and the drain line connection will be about two feet apart. My solution is to raise the cabinet top 1/2 inch with a plywood "deck" with cutouts for the sink and plumbing. Is 1/2 inch enough? Does anyone have other ideas?

Any comments are appreciated.



John Gayewski

In the Trades
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The illustration you have is unvented. The 30's were a different time. The general idea they are using is they have both sinks and dishwasher piped into a standpioe receptor. That may be legal in Texas which I think uses ipc, but it would still require the trap be vented,which your likley setup for.

For a kitchen sink the waste is very gross. The upc requires an air gap, but a lot of jurisdictions have written in the use of a high loop.

Seems like your getting through the challenges. Not sure what specifically you want to know.
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