Backflow is when the water in your pipes (the pipes after the water meter) goes backward (the opposite direction from its normal flow). There are two situations that can cause the water to go backward (backflow):

Backpressure – the pressure in your pipes is greater than the pressure coming in.

Backsiphonage – a negative pressure in one of the pipes.

To protect the water system, two kinds of backflow prevention assemblies (devices that prevent the backflow of water) are required for all business customers that present a potential hazard to the City’s water system:

External – to protect the City’s water from cross connection with the water on the customer’s premises  

Internal – to protect the customer from potentially hazardous cross connections in his own system.