Disposal on a double-bowl sink with a dishwasher: drain layout check (baffle tee, trap, slope, dishwasher loop)
On a double-bowl sink the disposal pumps water faster than a shared drain can take it, so badly laid out drains push water into the other bowl. The usual layouts tie the disposal discharge and the other bowl together with a continuous waste and a baffled (directional) tee above a single trap, with about 1/4 in per foot of slope on horizontal runs. The dishwasher drain goes to the disposal inlet or a dishwasher tee, with a high loop or an air gap as the local code requires. This guide is a layout check for the tech; drain piping changes beyond the trap are plumber work where your license or local code says so.
Before you start
- Power off the disposal (unplug or breaker) before touching the discharge or reaching near the drain opening.
- Turn the dishwasher off before disconnecting its drain hose; there may be standing water in it.
- Check local plumbing code (air gap vs high loop, trap arm length) with the authority having jurisdiction before rebuilding drain lines.
Diagnostic steps
Unlock all 5 steps with expected values
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