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Old 09-08-2009, 04:07 PM   #1
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dishwasher in Island new plumbing OLD HOUSE!

Ok so I have been working on an old farm house for longer than I care to admit.
It is time to tackle the plumbing. the main lin to the septic is cast iron. I am leaving the existing cast iron outside but replacing all galvanized inside.
The kitchen currently only has a sink. the drain goes into the crawlspace and straight out 4 feet where it Y's into the main line.

I want to add a dishwasher in to the island directly in front of the sink.
How should I drain and vent the dishwasher.
I would like to come off the main cast iron drain line into the crawlspace, pick up the sink and carry into the island and pick up the dishwasher.
is there a good way to draw a picture of this so you might have an idea what is in my head?
This is a really crude pic I drew with paint,
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Old 09-08-2009, 06:22 PM   #2
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for just a DW and no sink? i think a studor valve (air admittance valve) would work good in your case. simple to install. can even work temporarily while you work on a more elaborate (and probably not needed) solution.



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Old 09-24-2009, 12:29 PM   #3
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Installing a dishwasher in an island

You are on the right track. There are a couple different ways to install this appliance in an island. You can pick up a waste line from the main building drain in the crawlspace, as you talked about. The waste that serves the dishwasher should be trapped and vented. So, you can install an island vent. Below the floor at the dishwasher location install a horizontal wye fitting in the dishwasher drain line. Route the wye branch to the nearest wall and up that wall and through the roof to vent the dishwasher drain. Then, plumb the drain line from the wye fitting up through the floor, to a sanitary tee for the trap, up to the bottom of the countertop and then install in this order, a 45, a 90, and another 45. Take that line back down under the floor and tie it into the drain line just ahead of the horizontal wye. Install a p-trap and route the dishwasher drain into it through an air gap mounted on the counter. You can also install a Johnson fitting on a waste line brought up through the floor, then route the dishwasher drain from the air gap on top of the counter to the small tap on top of the Johnson fitting. You can also use the Johnson fitting on top of the p-trap if you want, to simplify connecting the dishwasher drain line to the waste line. The important concepts to remember in doing this installation is the appliance needs to drain through its own p-trap and it needs to be vented. Be sure to consult your local plumbing code for the installation requirements specific to your area.
Good luck!
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Old 09-24-2009, 01:42 PM   #4
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wow I am gonna have to re-read and draw that out. Sounds easy enough! . Thanks for the reply. Im not familiar with the Johnson fitting you mentioned..Ill have to research that as well.

Thanks for the replies
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