Smart sink switch or connected controller shows E4; disposal runs but water backs up into sink and drains slowly.

Safety first: Turn OFF the disposal and wall switch. Do not use chemical drain cleaners in a disposal-equipped sink.

• Step 1 – Check for standing water: If water is standing in the sink, do not run the disposal further. Remove excess water with a cup or small container.
• Step 2 – Inspect discharge elbow: Under the sink, locate the discharge elbow where the disposal connects to the drain. Place a bucket underneath, loosen the slip nut, and remove the elbow. Check for packed food debris and clean thoroughly.
• Step 3 – Check dishwasher inlet: If a dishwasher hose is connected to the disposal, remove the hose clamp and inspect the inlet nipple for blockage. If the disposal is newly installed, verify that the knockout plug inside the dishwasher inlet was removed.
• Step 4 – Clear P-trap: Remove the P-trap and adjacent drain pipes. Clean out any sludge or food buildup. Reassemble with new gaskets if needed and hand-tighten the slip nuts.
• Step 5 – Flush and test: Run hot water for several minutes, then briefly operate the disposal. If drainage is still poor, the blockage may be further down the household plumbing and a plumber may be required.