Know Your System
Supply Lines and Drain Lines Are Two Different Systems
People say “water line” and “sewer line” in the same breath, but they are opposite systems with opposite jobs — and confusing them leads to the wrong service call, the wrong diagnosis, and the wrong bill.
Water supply lines — this page — bring clean, pressurized water into the building: from the public main, through the meter, along your private line, and out to every fixture. Their failures announce themselves as leaks, pressure loss, and climbing bills.
Drain and sewer lines move wastewater out of the building by gravity alone. Their problems look like slow drains, gurgling, and backups. If that is your situation, you want sewer line repair — a different pipe with a different logic.
The practical test is simple: if water is coming out where it should not — a leak, a wet spot, a hissing pipe — you are in supply-line territory. If water is refusing to go away — slow, gurgling, backing up — you are in drain territory. This page is for the first kind.