How household plumbing works

Water enters through the service line and a meter, usually into an underground or ground-level sump.

A sump or ground-level tank stores water until it is pumped up to the overhead tank.

A pump moves water from the sump to the roof tank. Pressure pumps can also boost supply to individual floors.

The overhead tank supplies every floor. A float valve stops the inflow when the tank is full.

Ball or gate valves on the down-take and each branch let a plumber isolate part of the system for repairs.

The down-take pipe runs from the tank and branches off at each floor to bathrooms and the kitchen.

A water heater (electric, gas or solar) feeds a separate hot-water line. Hot lines need pipes rated for hot water.

Mixers blend hot and cold supply. Angle valves under basins and sinks allow each fixture to be isolated.

The kitchen sink takes a cold (and sometimes hot) supply, with a trap and waste pipe below.

Floor traps and fixture traps hold a little water to block sewer gases, while letting waste water through.

Vertical soil and waste pipes collect drainage from each floor. They are vented above the roof so water flows freely.

Chambers at changes of direction let the system be inspected and cleaned.