Did you know that public water system users share the responsibility of maintaining good water quality? It's true! There are things that homeowners can unintentionally do to compromise water quality, such as installing non-approved water connections on their plumbing systems, which are known as "cross-connections."

What is a Cross-Connection?

According to the State Water Resources Control Board's Cross-Connection Control Policy Handbook (CCCPH), a cross-connection is "an interconnection between a potable water supply and a non-potable source via any actual or potential connection or structural arrangement between a [public water supply] and any source or distribution system containing liquid, gas, or other substances not from an approved water supply." Cross-connections can compromise water quality when they are coupled with the occurrence of backflow.

What is backflow?

The CCCPH describes backflow as "the undesired or unintended reversal of flow of water and/or other liquids, gases, or other substances into a [public water system’s] distribution system or approved water supply." Backflow occurs when pressure on the downstream pipe is greater than the pressure upstream, causing water to flow in the reverse direction. Backflow can also occur from back siphonage or back pressure, which are similar phenomenons resulting from undesirable water pressure levels.

How Do Cross-Connections Impact Water Quality?

The existence of a cross-connection introduces the possibility for the backflow of contaminants and/or pollutants to occur in the public water supply. This is because any non-potable substances on the user's end could end up in the distribution system. That is why it is important that all public water system users avoid creating cross-connections on their property entirely.