Plumbing repair is no joke. It’s important that you understand your home or building’s basic plumbing scheme and the principles behind water delivery in your house.

Here are some basics of how your plumbing is likely laid out and how it works:
- From the city main, water enters underground through a ¾ or 1” metal pipe. For a pre-1950 house, the metal is usually galvanized plumbing-grade steel; after 1950, copper was used for the supply. Newer houses or houses supplied by a private water service (or M.U.D.) may often have polyethylene (PVC) pipes.
- Water usage will be metered by a city-owned metering device. If there’s not a meter inside the house, there’s probably one in a shallow pit between the house and the curb. You can lift the cover and read the meter to monitor your consumption in cubic feet (not gallons).
- There will be a shutoff valve next to the meter which can cut off all water going into the house. The cutoff valve can be turned with a pair of Channel-lok style pliers; in case of a major leak or other problem, you’ll need to know where this valve is to shut off the flow and prevent any damage.
- The hot and cold water lines that supply your sinks, toilet, etc. are called “trunk lines” and are usually ¾” in diameter. The pipes to outdoor hose faucets and other high-demand plumbing fixtures are also usually ¾” in diameter.
- Each plumbing fixture (toilet, sinks, bathtub, etc) should have a cutoff valve of its own. That way you can cut off the supply to that particular fixture for repair without having to cut off the water for the entire house.
- City water supplies usually have a pretty fair amount of pressure. The weight and force of water can be something to reckon with; make sure that you take this into account during any plumbing repairs or maintenance so that you don’t wind up with a huge mess on your hands.