A toilet that runs continuously wastes water and also:

A continuously running toilet is a failure of one of two components, and knowing which lets the report name a correctable defect rather than an annoyance. A flapper that no longer seals lets tank water leak into the bowl; the level drops, the fill valve senses it and refills, and the cycle repeats indefinitely. A fill valve that fails to shut off does the same thing from the other direction, sending water over the overflow tube continuously. Both are inexpensive parts and both waste a substantial volume — a leaking flapper can pass thousands of gallons a month without any visible sign in the bowl. The inspector reports the observation and the likely component, which is enough for the client to act without a plumber diagnosing it first.

Continuous running points to a flapper that no longer seals or a fill valve that fails to shut off. Both are correctable component failures, so the report names them as the likely cause rather than treating the running as a quirk.

A toilet tank refills when the water level drops. A deteriorated flapper leaks tank water into the bowl, and a failed fill valve overflows into the overflow tube; either causes the fill cycle to repeat continuously. Both are common, inexpensive repairs.

Leaks Down or Never Shuts Off. Water escaping the tank means the flapper; water arriving without stopping means the fill valve. Two parts, one symptom.

Dye in the tank confirms a flapper leak — colour appearing in the bowl without a flush is diagnostic and takes a few minutes while you inspect elsewhere.

• •Treating a running toilet as harmless because water is not visible on the floor
• •Attributing a single fixture's behaviour to house supply pressure
• •Reporting the symptom without naming the likely component