Notice the signs
Observe
Note which basin fills, whether a disposal changes the level, when dishwasher water appears, how quickly the sink recedes, other affected fixtures, recent food or grease event, and previous chemical or mechanical work.
Note 27
Place the condition before choosing the work
Protect the room
Safety line
Cut power before any authorized disposal inspection and keep hands out of the chamber. Do not combine drain products, repeatedly run an appliance into a backup, or loosen a full trap without safe containment.
Material note
Local boundary
The visible sink assembly is private plumbing, but a wider branch problem may require different access and property-system verification. Appliance repair and cabinet damage should not be hidden inside a drain-clearing price.
Service flow
Written scope
Ask which fitting or cleanout will be used, how the cabinet is protected, whether the disposal or trap is removed, what method fits the pipe, when a camera adds value, and who reinstalls every connection.
Close the loop
Verification
Fill and drain both bowls under observation, run the disposal and dishwasher connection only when safe, inspect the trap and cabinet afterward, and record whether downstream fixtures stayed quiet.
Current primary source