Garbage disposal runs but water and waste do not drain; water backs up into the sink.

Safety first: Turn off power to the disposal and do not run it while the sink is backed up; this can force leaks at seals.

• Check the discharge elbow: Place a bucket under the disposal outlet. Loosen the discharge elbow clamp or screws and remove the elbow. Clear any compacted food waste using a bottle brush or flexible drain brush.
• Clean the P-trap: Remove the P-trap under the sink and clear sludge or food build-up. Rinse thoroughly before reassembly.
• Dishwasher knockout: If the dishwasher is newly connected and not draining, ensure the plastic knockout plug in the Rangemaster disposal's dishwasher inlet has been removed. Use a screwdriver and hammer to knock it out, then retrieve the plug from the grinding chamber.
• Reassemble and test: Refit all pipes, ensure gaskets are seated, then run cold water and briefly operate the disposal. Check for leaks at all joints.