What is backwashing?

• A. Exchanger tubes that have been eroded are cleaned by reversing the flow to knock off rust.
• B. Exchanger tubes cleaned by forward flow with detergents.
• C. Replacing tubes after corrosion.
• D. Line flushing with high-velocity water.

Answer: (A)

Backwashing is cleaning by reversing the flow through a filter or exchanger so that fluid moves backward through the media or tubes. This reversed flow lifts and carries away accumulated deposits—such as rust, scale, or sediment—that have built up on the surfaces, helping restore normal flow and heat transfer performance. It differs from cleaning with forward flow and detergents, replacing tubes, or flushing lines forward at high velocity. In practice, valves are used to reverse the flow just enough to flush the deposits out of the system.