What is the correct/best plumbing arrangement for a kitchen sink DWV with; a double bowl sink, a garbarge disposal, and a dishwasher drain. Everyone I know offers a different opinion, but they’re not experts.
I am presently renovating my kitchen and having had problems in the past with the garburator sink backing up when the dishwasher drained into a garbage disposal that “someone” had forgot to run, and/or the adjacent sink backing up when the disposal runs a large batch.
The present arrangement has the main sink 1-1/2″ ABS drain with only an elbow (no trap) draining into a tee dropping down from the adjacent garbage disposal bowl (the dishwasher drains into the disposal) and all this running thru the only trap to the DWV stack about 24″ away. The drain slope seems adequate.
Should there be a trap for each sink? Would the dishwasher drain better into a separate tee? Would an air gap be beneficial for this (one is not code in the area)?
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In the beginning there was Breaktime...
With all that "backing up" i'd suggest cleaning the drain pipe while you have everything apart.
For kitchen sinks we have a disposal (dw drains into that) on one side and a regular strainer on the other side.
Those go into a tee that then enter a p-trap then into the main drain.
I'm sure someone will be along soon to tell you how wrong that is, but we get no complaints.
Family.....They're always there when they need you.
OK let's first start with the code.
Only one trap per trap arm is permitted (not that I agree with that code) so if there is only one stub out of the wall then you can only have one trap.
Dishwashers must drain upstream of a garbage disposal, or you run the risk of a garbage disposal pushing waste water back up the dish washer drain line.
The two bowls tie together with a "directional tee" when a garbage disposal is present.
The "best way" IMO is the the dw drains into the inlet provided for on the gd.
The gd turns down directly towards the trap.
The directional tee is placed on that vertical section with the branch picking up the other bowl.
That helps prevent the gd backing up into the other sink.
In this pic the gd goes into the top of the directional tee ( directional tee will have a baffle in it to direct the flow) & the other sink will connect via the 90 degree elbow.
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I hate to tell you this.But poor Clive died 6 years ago while waiting for your answer..
William the Geezer, the sequel to Billy the Kid - Shoe
Man did I get suckered into one of rez's bumps from the grave ;-)