Plumbing in Philadelphia is a stack in a rowhouse. Baths line up, the kitchen may sit under a bath, and a wet ceiling is often the fixture above you. Galvanized supply, old angle stops, and cast stacks are common. The main may be in the basement you enter from the stoop. Flat-roof leaders sometimes join the drains, so a storm shows up indoors. The street is flat and the lots are tight. There is no hill lateral to blame until you have described the stack.
Choose leak, drain, or water heater. A supply leak at a valve you can reach is one call. A tub that backs up only when the upstairs bath drains is the stack. A water heater in a low basement that is leaking onto the floor is the third, and it is urgent if the floor is already the low point of the house. If trouble starts only in hard rain, say so. That may be a leader, a sewer backup, or a basement drain, not the kitchen faucet.
Old metal fails when disturbed. Do not crank every stop. Describe brown water, a chase that is damp, a ceiling bubble, a heater that no longer makes hot water. If the basement fixture gurgles when the street is flooded, say that plainly. Shared rows mean your clog and the neighbor's tub can be the same pipe. Mention whether their side is slow too, if you know. Access for a heater replacement is the stair and the sidewalk.
Have tank or tankless, gas or electric, and whether the heater is wet or just tired. Say if a drain was snaked and came back the same month. Say who lives under the leak. Ask about the vent, the pan, and who patches plaster. A cable clears a clog. It does not rebuild a stack or regrade an alley. Point at the failure. If you cannot find the main, say that before the call becomes a tour.
Row plumbing is vertical. Plumbing in Philadelphia starts with the floor above, the basement under the stoop, and the rain that should have stayed on the roof. Call the number on this page.