{"id":25,"date":"2025-09-23T04:42:30","date_gmt":"2025-09-23T09:42:30","guid":{"rendered":"https:\/\/plumbing101.i234.me\/wordpress\/?p=25"},"modified":"2025-09-23T04:42:30","modified_gmt":"2025-09-23T09:42:30","slug":"how-to-plumb-a-double-sink-disposal","status":"publish","type":"post","link":"https:\/\/plumbing101.i234.me\/wordpress\/how-to-plumb-a-double-sink-disposal\/","title":{"rendered":"How to Plumb a Double-Sink Disposal"},"content":{"rendered":"
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How to Plumb a Double-Sink Disposal (plumbing101.i234.me)<\/a><\/strong><\/p>\n<\/header>\n
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Question<\/h2>\n

I am installing an InSinkErator Badger 5 (1\/2 hp) under a double sink. There is no dishwasher. The disposal outlet lines up with the horizontal pipe that feeds a tee, then a single P-trap, then the wall drain. The manual mentions two traps. The disposal also features a 90-degree discharge tube that directs the flow downward. I want to avoid major rework. Can I keep everything horizontal and avoid vertical changes? Are there basic double-sink disposal layouts? Drawings would help.<\/p>\n<\/section>\n

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Answer<\/h2>\n

You seldom want two traps on a double sink. Use one P-trap serving both bowls through a \u201ccontinuous waste\u201d kit with a baffle tee. That layout prevents siphoning and is the standard method in many jurisdictions. Mount the Badger 5 on one bowl. Rotate the disposal\u2019s discharge elbow sideways so it aims toward the baffle tee, not straight down. Keep a slight downward slope on the short discharge run. Aim for roughly 1\/4 inch per foot. Connect the non-disposal bowl to the other side of the baffle tee. Place the single P-trap after the tee and run it to the wall drain.<\/strong><\/p>\n

Why not two traps? Two traps on one drain arm can self-siphon. That can pull water from a trap and let sewer gas in. A single trap with a baffle tee balances flow from both bowls. It also makes snaking and cleaning easier.<\/strong><\/p>\n

Parts you will likely need: a continuous waste kit with baffle tee, a 1-1\/2 inch P-trap kit, slip-joint nuts and washers, and the Badger 5 discharge tube. If alignment is off by half an inch or so, use a short flexible discharge tube made for disposals. Avoid long corrugated sections that can catch debris.<\/strong><\/p>\n

Basic steps: 1) Hang the disposal with the mounting ring and flange. 2) Dry-fit the discharge elbow so it points toward the tee. 3) Build the continuous waste between bowls. 4) Place the single P-trap after the tee. 5) Adjust for slope and alignment. 6) Tighten slip joints hand-tight, then a quarter turn with pliers. 7) Leak-test with both bowls running. 8) Run the disposal with cold water and check again.<\/strong><\/p>\n

Tips: Keep the trap weir below the wall stub by an inch or more. Do not trap the dishwasher stub; you do not have one here. Avoid \u201cS-traps.\u201d Keep all slip-joint washers facing the right direction. Use plumber\u2019s putty on the sink flange if required by the manual. If the wall drain is too high for a proper P-trap, you will need to open the wall and lower the trap arm.<\/strong><\/p>\n

Helpful visuals and manuals are linked below. They show the single-trap, baffle-tee layout. That is the cleanest, most forgiving setup for a double sink with a disposal.<\/strong><\/p>\n

External resources:
\nBadger 5 install manuals<\/a>,
\nstep-by-step disposal guide<\/a>,
\ncode resources<\/a>, and
\nflex discharge tube<\/a>.<\/p>\n<\/section>\n