When a restaurant floor drain or sink backs up during service, the first priority is to control water use and keep the overflow from spreading while you identify the affected area.
Stop water use that makes the backup worse
If dishwashing or another high-flow fixture causes the floor drain to rise, pause that use until the cause is clearer.
Check whether one or several fixtures are affected
A single slow sink and several drains backing up at once point to different possible causes. Note every affected location.
Do not assume every problem is at the surface
Restaurant grease can build up farther down a branch or main line, especially when the same issue keeps returning.
Information to have ready
When you call, provide the address, type of business, affected fixtures, when the backup started, whether drainage has stopped completely, and whether the line has been cleared before.