Water Service Connections
In this diagram, there are two separate connections to the public water system distribution system, the fire sprinkler system and the domestic potable water system connection. Having two separate connections is the preferred arrangement for the reason being that the potable system can be shut down for repairs, meter installations or for non-payment of the water bill without shutting down the fire sprinkler system.
On the left is the fire sprinkler system service line connection. This connection is a cross-connection between the public water system potable water and the non-potable fire sprinkler system water. It is not metered and there is a curb stop valve located before the property line. To control this cross-connection, a backflow prevention device assembly shall be Installed upstream of the fire alarm check valve. The installation of this backflow prevention device assembly would be considered a containment installation. The type of device assembly would be based on the degree of hazard of the non-potable water.
To the right of the fire sprinkler service line connection is the domestic potable water system service line connection, which is metered and has a curb stop before the property line. This connection to just after the water meter is not a cross-connection because it does not meet the definition of a cross-connection since there is no connection to a non-potable water supply source. Plumbing codes require potable water to every structure with plumbing fixtures that provide water for drinking, bathing, culinary purposes, and food processing, medical or pharmaceutical products. Since a cross-connection does not exist, no backflow prevention device for cross-connection control is required or necessary. However, the public water system by ordinance may require a backflow prevention device assembly for “service line protection” to be installed directly after the meter. The installation of this backflow prevention device is for hydraulic purposes only since it prevents the reversal of the domestic potable water system into the public water system that is potable. The service line protection device is controlling the reversal of flow between two potable water systems.
The potable water after the meter within the domestic piping system may have cross-connection but they should all be controlled by air gaps or mechanical backflow prevention devices pursuant to the plumbing codes. Controlling cross-connections where they exist after the meter is known as isolation protection.