If a sink overflows after being used to wash dishes, even if the running water was not left on continuously, there could be several possible reasons for this:
Clogged drain: If the sink's drain is partially or fully clogged, the water may not be able to flow out properly, leading to an overflow. Over time, debris like food particles, grease, or soap scum can accumulate in the drain and cause blockages.
Slow-draining pipes: If the pipes connected to the sink are partially obstructed or have a reduced flow capacity, water can back up and overflow the sink. This could be due to mineral deposits, scale buildup, or other debris in the pipes.
Improper venting: Plumbing systems typically include vent pipes that allow air to enter and exit the drainage system, helping to maintain proper pressure and prevent blockages. If the vent pipe is blocked or improperly installed, it can impede the flow of water and lead to an overflow.
Faulty plumbing or pipe damage: If there is a leak, crack, or damage in the plumbing system, it can cause water to escape and overflow the sink. This could be due to deteriorated pipes, loose connections, or faulty plumbing fixtures.
Insufficient slope or incorrect installation: Proper installation of the sink and its plumbing is crucial to ensure that water flows smoothly. If the sink or pipes are not installed at the correct angle or slope, water may accumulate and eventually overflow.
If you're experiencing recurrent issues with sink overflow, it may be best to consult a plumber or a professional in the field to assess the specific situation and provide appropriate solutions.