What is backflow? Water distribution systems are designed with the intention of water flowing in one direction - from the supply point to the consumer. However, conditoins arise from either the supplier or the consumer that deviate from the "normal" conditions causing water to flow in the opposite direction. This is called Backflow!
What is backpressure? The pressure on the consumer side is greater than the supply side. A good example is a car wash or where pumps are used which creates higher pressure than what the city supplies.
What is backsiphonage?
The pressure on the supply side is lower than the consumer side. A good example is a city water main break where the water will flow backwards from the consumer to the main break.