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Dishwasher water comes up in the sink when the disposal runs
What would help narrow down a sink backup that happens when the garbage disposal runs? Does it point more toward a blockage at the disposal outlet or farther along the shared drain, or could the dishwasher hose routing or sink drain setup be involved?
Would it matter whether the dishwasher is running or has just drained, and whether water rises in one basin or both? I’m also curious what hose or air-gap details are safe to check without disconnecting plumbing, and when it’s better to stop using the disposal and call a plumber.
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2 replies
If the disposal alone triggers the backup, that points toward a restriction in its outlet or the nearby shared drain, but doesn’t locate it. Water rising in both basins makes a restriction farther along their common drain more plausible; one-basin backup can fit a more local branch issue. If it happens around dishwasher drainage too, note that timing: a backed-up dishwasher discharge may also involve the shared drain or hose routing. Those patterns narrow possibilities, not confirm a diagnosis.
Without taking anything apart, you can look for a visible dishwasher hose that’s kinked, crushed, or leaking, and - if there’s an air gap on the sink or counter - check whether its cap looks obstructed. Don’t disconnect the hose or put a hand into the disposal. If water is backing up or leaking, stop running the disposal and dishwasher until the cause is checked; a plumber can inspect the drain safely.
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