Notice which fixtures are affected
A single slow sink and several backing-up fixtures describe different situations. Make a note of where the problem occurs before requesting service.
Mention repeat problems
Tell the plumber if the same issue has returned after previous work. Include unusual drain noises or changes that happen when another fixture runs.
Discuss the next step
The appropriate cleaning or repair depends on the affected part of the system. Ask what will be assessed and what the proposed scope includes.