Plumbing in New Jersey fails along familiar local lines: older supply in dense blocks, freeze on inland outside walls, and basements that take water when the rain is hard. Two-families share stacks. A leak in the ceiling may be the bath above. A shore house adds corrosion and outdoor fittings that have lived in salt air. A sump that quits during a nor'easter is its own emergency. Say whether water is moving right now and whether you can reach a shutoff.
Split the job in the first sentence. Supply leak, drain backup, or water heater. A drip at a valve is not a cellar filling from the floor drain. A water heater leaking at the tank is not a slow lavatory. If the heater sits in a basement that has flooded before, say that. If the only shutoff you know is behind stored boxes, say that too. Do not open a wall to explore. Describe the fixture and the floor.
Freeze is real away from the warmest coastal pockets. Hose bibs left charged, kitchens on outside walls, and houses that lost heat will split a line and then show the damage at the thaw. In older cities the specialty is age: galvanized lines, valves that fail when touched, and cast stacks. Heavy rain adds a third pattern, when a low drain or a basement fixture backs up. Say if the trouble happens only when the sky opens. That splits a sewer or storm issue from a supply leak.
Have the heater details if that is the complaint: tank or tankless, gas or electric, still making hot water or actively wet. Say if a drain was cleared and came back. Say if you are in a flat and the main is in a cellar you do not control. Ask about the vent, the pan, and who patches a ceiling. A cable clears a clog. It does not fix a broken pipe or a grade problem outside. Say which mess you see.
A shared stack, a frozen bib, and a shore fitting full of salt are different calls. Plumbing in New Jersey starts with where the water is and whether you can stop it. Call the number on this page.